"Add a pop of colour."

It's one of the most repeated pieces of design advice out there.

And when every new-build comes in all-white or millennial grey, sure, some colour makes sense.

When done well, it brings a flat room to life and gives the eye something to land on.

But it's really easy to get wrong.

Most people pick a colour they love, scatter it around the room, and wonder why things still feel… off. Flat. Like something's missing.

They followed the advice. They add a colour. So what went wrong?

Usually one of these three things.

1. Everything matches, and that's the problem

Say you fall in love with blue. Great choice. So you buy a couple of blue cushions. Then a set of blue chairs. Then a blue curtain.

And then the blue does absolutely nothing.

Here's why.

The whole point of an accent colour is to give a mostly neutral room some life.

But when that colour appears in the exact same shade, on the exact same type of object, with no variation in tone or material, it just falls flat. There's no depth and no richness.

It's not that you used too much of it. It's that you duplicated it instead of varying it.

And that's a big difference.

2. Repetition works, but only with variation

This is the bit most people miss.

You absolutely should repeat your accent colour around the room. I'd say at least three different objects. One lonely blue cushion on a neutral sofa just looks like it was left behind after a party.

The trick is that each repetition needs to be different.

Heidi Caillier Design

Look at the rooms above. The blues appear on the rug, cushions, an armchair, dining chairs, books, and even small decor pieces. The greens run through the sofa, a lampshade, wallpaper, and plants. That's a lot of repetition — but none of it feels flat, because every instance is a different shade, a different material, a different scale.

That's what makes it feel layered and intentional instead of like you bought a matching set.

Here's what to keep in mind:

• Vary the shade. Light, mid, and deep tones of the same colour family. Not three cushions in the exact same navy.
• Use different materials. Ceramic, linen, paint, velvet, wood. They all carry colour differently, and that's what creates richness.
• Play with scale. A large artwork hits differently than a small vase. Mix big moments with small ones.
• Spread it across the room. Don't cluster your accent colour in one corner. Distribute it vertically and horizontally — something down low like a rug, mid-level like a cushion, up high like a piece of art.

And a personal rule of mine: never buy more than two of the exact same cushion. Mixing them forces variation, and variation is what makes a room look curated.

3. Your accent colour needs something to push against

An accent colour doesn't work in isolation. It works because of what surrounds it.

This is where the 60-30-10 rule earns its place. 60% dominant colour (walls, large rug, main sofa). 30% secondary (curtains, a key piece of furniture, bigger accessories). 10% accent.

But those percentages aren't just about proportion. They're about contrast.

Photo by Nicki Sebastian (left) & Heidi Caillier Design (right)

A warm accent needs a cooler base to push against. A cool accent needs warmth behind it.

Some combinations that follow this logic:

• Warm cream walls + deep green sofa + organic wood and earth tones
• Warm peach walls + cool navy bed + brass and walnut accents
• Cool white walls + warm oak and tan leather sofa

The "add a pop of colour" advice isn't wrong. It's just incomplete.

Colour works when it's varied enough to stay interesting, restrained enough to stay meaningful, and placed where it can actually do something.

If you want to go deeper on colour, I covered them in this playlist​

Cheers,

Reynard