Basics of Interior Design Colour Theory | Everything You Need to Know About Colours!

Choosing colours for your home can feel like opening a can of worms. One minute you’re confident about navy blue, and the next you’re crying into a pile of colour swatches because every shade of grey looks exactly the same.

But don’t stress—this guide is here to help.

We’re breaking down Interior Design Colour Theory in the simplest way possible. No design jargon. No overwhelming colour wheels. Just clear, practical tips to help you choose colours with confidence—and maybe even enjoy the process a little.

Think of this as a beginner-friendly guide. As a designer, I still revisit these basics from time to time. But after years of experimenting in real homes, I’ll be honest—I don’t always follow every rule. Design, after all, is about feel as much as formulas.

So if you’re already a colour expert looking to push creative boundaries, this might feel a little too safe. But if you’re just trying to figure out what colours actually go together—this one’s for you.

Hi 👋 I’m Jacqueline from The Glade Design. I specialise in residential interiors. Check out my services or email me to chat. New design tips and home inspo every week—subscribe for exclusive content!

Some links in this post are affiliate links — if you buy through them I may earn a small commission at no extra cost to you, and you get a discount for using the link.

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What Is Interior Design Colour Theory?

Put simply, Interior Design Colour Theory is the “how and why” behind choosing colours that look good together in a room.

It helps you make sense of questions like:

• “Do these colours clash or complement each other?”
• “Why does my beige wall suddenly look pink in the afternoon?”
• “How many colours should I actually be using in one room?”

Understanding just the basics can take the stress out of everything—from picking throw cushions to choosing your wall paint. You’ll feel more confident, make fewer expensive mistakes, and actually enjoy creating a space that feels right. Colour is one of the seven elements of interior design, and it behaves the way it does because of the principles sitting underneath all seven — so if this guide leaves you curious, those two are the natural next read.

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Step 1: Meet the Colour Wheel

The colour wheel is your best friend when it comes to understanding how colours work together. It’s a simple circle that shows how different colours relate—and it’s the starting point for almost every colour decision in interior design.

Here’s the basic breakdown:

• Primary Colours – Red, blue, and yellow. These are the foundation colours—you can’t make them by mixing anything else.
• Secondary Colours – Orange, green, and purple. These are made by mixing two primary colours together (like blue + yellow = green).
• Tertiary Colours – The in-betweeners, like teal (blue-green) or coral (red-orange). These are made by mixing a primary with a secondary colour.

Knowing where colours sit on the wheel helps you pair them in ways that actually work—and stops your space from turning into a rainbow gone rogue.

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Step 2: How to Put Colours Together

Here’s where Interior Design Colour Theory really comes in handy. These are the five most common ways to build a colour scheme that actually works.

1. Monochrome – One colour, different shades

Think light grey walls + medium grey sofa + charcoal cushions. It’s easy and looks calm and stylish.

2. Analogous – Colours that sit next to each other on the wheel

Like green, blue-green, and blue. They feel soft and relaxing together.

3. Complementary – Colours directly opposite on the wheel

Think blue and orange. They pop against each other. Use one as your main colour and the other as a fun accent.

4. Split-Complementary – A little more variety

Pick a colour, Then look at the colour directly opposite it on the colour wheel. Instead of using that exact opposite, use the two colours next to it

5. Triadic – Three colours evenly spaced out

Red, blue, and yellow is a classic example. Great for a fun, colourful vibe—but you need to balance it well.

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Step 3: Warm vs Cool Colours

Colours aren’t just about how they look—they change how a room feels. Some colours feel warm and cosy, while others feel cool and calming.

The tricky part? Telling the difference—especially with whites!

If you’re ever unsure whether a colour is warm or cool, try this:
👉 Hold it up next to plain white printer paper. The undertone will show up more clearly—warm colours will look a bit yellow or pink, cool colours will lean blue or green. Whites are the worst offenders here, which is why I wrote a whole post on the seven Dulux whites I actually use and why the undertone matters far more than the name on the tin. And if you’re six near-identical swatches deep and getting nowhere, undertones are one of the things a 90-minute design consultation settles in about ten minutes.

Here’s the quick breakdown:

• Warm colours (like red, orange, and yellow) feel inviting, cosy, and energetic. Great for living rooms or social spaces.
• Cool colours (like blue, green, and purple) feel fresh, calm, and relaxing. Perfect for bedrooms and bathrooms.
• Neutrals (like white, grey, and beige) can go either way—depending on their undertones.

💡 Designer tip:
If your room gets lots of natural sunlight, cool colours can help tone it down.
If your room feels dark or cold, warm colours will make it feel cosier and more inviting.

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Step 4: How Many Colours Should You Use?

Here’s a super simple rule that designers use all the time—it’s called the 60-30-10 rule. Think of it like a recipe for a well-balanced room.

• 60% – Main Colour: This is your base. Usually used on walls, large furniture, or flooring.
• 30% – Secondary Colour: This supports your main colour. Think curtains, rugs, bedding, or feature furniture.
• 10% – Accent Colour: This is your pop of personality—used in cushions, artwork, vases, or lighting.

💡 Tip:
You don’t need five different colours for a room to feel “designed.” Just two to three well-chosen colours can create a space that feels cohesive, stylish, and intentional.

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Step 5: Colour and Mood

Every colour makes you feel a certain way. That’s why Interior Design Colour Theory includes a bit of psychology too.

Here’s a quick cheat sheet:

Colour	Feels Like	Good For
Blue	Calm, fresh	Bedrooms, bathrooms
Green	Balanced, natural	Living rooms, kitchens
Yellow	Cheerful, warm	Kitchens, offices
Red	Bold, energetic	Dining rooms, entryways
Pink	Soft, playful	Nurseries, bedrooms
Grey	Calm, neutral	Anywhere (if the tone’s right)
Black	Dramatic, sleek	Accents, handles, lighting
White	Clean, airy	Small or dark spaces

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Step 6: How to Use Colour in Real Homes

Let’s look at some examples. If you want the long version for one particular room, I’ve written full guides on choosing living room colours and on kitchen colour schemes and cabinet colours.

Living Room

• Use a neutral base like beige or grey
• Add colour with cushions, art or a rug
• Keep it cosy with warm-toned lighting

Bedroom

• Stick with soft, relaxing colours (blue, green, lilac)
• Try deeper tones on a feature wall if you want a moody feel
• Add texture with linen, timber, and soft lighting

Kitchen

• Mix classic (white, grey) with a pop of colour in your splashback or stools
• Add warmth with brass handles or timber shelves
• Don’t forget lighting—it changes how colours look!

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Mistakes to Avoid

Even if you understand all the basics of Interior Design Colour Theory, it’s still easy to slip up—especially when you’re scrolling through Pinterest or admiring a designer’s perfectly styled home.

One important thing to remember:
Don’t try to copy well-known designers or Instagram homes exactly.
Their colour palettes often look amazing in photos—but they can be tricky to pull off in real life. That’s because:

• The colours you see online are usually edited or filtered
• Designers aren’t just using colour—they’re layering in texture, lighting, materials, and styling tricks that change the whole look

So, if you’re working on your own home and not feeling super confident with colours just yet, that’s totally okay. Start simple—and keep an eye out for these common mistakes:

❌ Choosing paint first
Always pick your major furniture, flooring, or fabrics before you choose paint. It’s way easier to match paint to your sofa than the other way around.

❌ Forgetting about lighting
Colours can look completely different in morning light, afternoon sun, or under warm light bulbs. Always test samples on your wall—and check them at different times of day.

❌ Using too many colours
Trying to cram five or six colours into one space can feel messy. Stick to two or three that work well together, and repeat them throughout the room.

❌ Copying Pinterest without thinking
Just because it looks great in someone else’s home doesn’t mean it’ll work in yours. Think about your own space, lighting, and what makes you feel good.

💡 Bottom line:
Start simple, build slowly, and focus on creating a space that suits your lifestyle—not just your Pinterest board. If something about the colours feels off to you—it probably is. Trust your gut. And if your gut says something is wrong but you can’t name what, that’s the moment to book a consultation rather than buy four more sample pots.

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Bonus: How to Be Eco-Friendly with Colour

Good news—your colour choices can be sustainable too:

🌿 Use low-VOC (low-toxin) paints
🌿 Support Australian eco-friendly brands
🌿 Upcycle or repaint furniture instead of buying new
🌿 Choose colours you’ll love long-term to avoid redoing things

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Feeling a Bit Stuck?

If choosing colours still feels like a guessing game, don’t worry—you don’t have to do it alone.

Book a Colour Consultation

I offer simple, personalised help to take the stress out of colour picking. Whether you need a quick opinion or a full home colour plan, I’ve got you covered.

👉 Click here to book a session

Or check out my done-for-you colour scheme packages—designer-created palettes with suggested materials and colours that go together beautifully. It’s like having a mini designer in your pocket.

Timeless Scandi Interior Colour Scheme

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Interior Design Colour Theory it’s really just about understanding how colours work together—and how they make you feel.

You don’t need to follow every rule. But once you know the basics, you’ll feel so much more confident choosing colours for your space. And honestly? You’ll probably start enjoying it too.

So go on—pick that paint swatch. Mix those cushions. And create a space that looks (and feels) like you.

One honest caveat before you go. Colour is the easy half of a room — paint is cheap, a cushion is cheaper, and both can be undone on a Saturday. If a room still feels wrong once the palette is right, the problem usually isn’t the colour at all, it’s where things sit. That’s what my Fix My Floor Plan service is for: $297 a room, no meeting required, and you get a layout that works before you spend another cent on paint.

Did you know that working with an interior designer comes with special supplier discounts? Here’s a treat for you! Shop bathware at The Blue Space through my link. There’s a discount attached to that link — how much depends on the product, and there’s no code to type in, it comes through the link itself. Worth saving it somewhere if a bathroom is on the cards later on.

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