Dopamine interiors with interior designer Justine Guillermou

When interior design meets joy, colour and personality, something magical happens: a space stops being just “some walls and furniture,” and becomes a vivid extension of who we are.

That’s the philosophy behind Rainbow Shaker, the bold, playful interior-design studio founded by Justine Guillermou. Based in East London, Justine brings a unique energy to interiors: she doesn’t just decorate, she transforms. Rainbow Shaker’s aesthetic is all about colour, creativity and emotion. From the “Colour Your Home Happy™” course to full home renovations bursting with retro palettes and joyful patterns, Justine specialises in turning blank, generic spaces into homes filled with life, memory and character.

In this conversation, we dig deep into what it really means to design for happiness: how colour, art, memory and architecture intersect, and how even the most reluctant decorator can bring warmth, personality, and soul into their home.

What does “bringing colour and happiness into a home” truly mean for you?

For me, it’s not about making homes “bright” for the sake of it. It’s about helping people feel seen in their own space. Colour is a language: when it’s used intentionally, it can support your mood, your energy, your memories, even your confidence.

Bringing colour and happiness into a home means creating a space that feels alive, comforting, and deeply personal. A place where you exhale when you walk in. Where your home works with you, not against you.

How does your background (French, engineering turned creative, living in East London) influence your style and approach to interior design?

All of it shapes the way I work.

My engineering background gave me structure, logic and problem-solving skills; I’m very methodical behind the scenes. My French roots bring a sensitivity to colour, art and emotion (and maybe a bit of a critical mind sometimes 😉). And living in East London keeps me curious, playful and unafraid of boldness.

So, my work often sits at the intersection of intuition and structure: joyful, expressive spaces that are also deeply functional and thought-through. Colour with intention, not chaos.

When you start a project, how do you decide which colours, patterns or artistic elements best reflect the inhabitant’s identity and emotions?

I always start with people, not palettes.

I ask questions about their life, their memories, how they want to feel at home, what energises them, what soothes them. Often, the clues are already there: in their travels, music, clothes, childhood memories, or even the way they describe their “happy place”.

Then I think about how they live or how they want to live. I mentally put myself in my client’s shoes and retrace their daily routine, asking questions like: What happens here every day? Where do they slow down? Where do they need energy? This helps me naturally define zones and functions.

From there, colour becomes a tool to translate emotion into space. The goal isn’t to impose my taste, but to reveal theirs, sometimes even before they fully realise it themselves.

How do you view the role of art in interior design — as a finishing touch, or part of the plan from the start?

Always part of the plan 😊

Art shouldn’t feel like an afterthought hung on an empty wall. It can shape the colour palette, the rhythm of a space, the emotional anchor of a room.

Whether it’s a painting, a sculpture, a handmade object or even something sentimental, art gives a space its soul. I often design around it, not on top of it.

Are there colours that are universally more likely to bring joy, or does it all depend on people’s preferences? And are there any colours you never use?

Some colours tend to carry similar emotional weight: yellows often feel uplifting, blues calming, greens grounding. But joy is deeply personal.

A colour that feels energising to one person can feel overwhelming to another. Context matters: light, proportions, pairing, memory.

There are no colours I never use, only colours I use carefully. Even neutrals can feel joyful when done right. It’s never about banning colours, it’s about using them with intention.

What’s the connection between nostalgia, memory, and interior design, in your view — and how do you incorporate that into your work?

Memory is one of the most powerful design tools we have.

A colour can instantly transport you to a holiday, a childhood room, a feeling of safety or freedom (like a Proustian madeleine). When design taps into that, it becomes emotionally grounding.

I often incorporate subtle references: a palette inspired by a place someone loves, a material that reminds them of home, an object that carries a story. These elements create spaces that feel meaningful, not generic.

Can you share an example of a project where joyful design truly transformed the mood of a space — or the life of its residents?

One that stays with me is a family home that was beautifully maintained but entirely grey. My client described it as “depressing”, especially in winter.

We introduced warm, joyful colours inspired by a family holiday memory and suddenly the house felt alive. She later told me it had a real impact on her mental health and that she actually looked forward to being at home again.

That’s when you realise design isn’t superficial. It can genuinely change how people feel day to day.

How does your “Colour Your Home Happy™” course help people express their personality and emotions through design — even if they don’t consider themselves creative?

Most people aren’t “bad at colour”, they’re just scared of getting it wrong.

The course removes that fear. It gives people a clear, reassuring framework to understand colour emotionally and practically, without jargon or pressure.

I guide them step by step, helping them trust their instincts, connect design choices to their own memories and lifestyle, and realise they are creative, they just needed the right language and support.

Finally, from your experience: does a home designed with colour, personality and art affect daily wellbeing, mood, or even relationships? Why?

Absolutely.

Our homes are the backdrop of our lives. When a space supports who you are, it reduces friction, stress and fatigue. It invites joy, connection and presence.

Colour and personality make a home feel lived-in, welcoming, human. And when people feel comfortable and grounded in their environment, it naturally impacts mood, energy and even how we relate to others.

Design isn’t just about how a space looks, it’s about how it makes you feel, every single day.

Thanks to Justine for taking the time to answer all my questions. It was very insightful.

Talking with Justine reminds me that interior design is so much more than decoration: it’s storytelling, self-expression and emotional alchemy. Through Rainbow Shaker, she proves that homes don’t have to be a “safe” mould, they can radiate colour, personality and joy.

Whether you’re renting a small flat, redesigning a whole house, or just curious about turning beige into bold, the path to a happier, more alive home doesn’t start with trend charts or rules. It begins with you: your memories, your emotions, your soul.

So, if you feel drawn to colour, nostalgia, art or simply something different, trust your instinct. Because, as Justine shows, a splash of colour can transform a wall, and a thoughtful design can transform a life.

And take a look at her online course which I have done myself and found extremely useful:

Colour your home happy course

You can also find Justine on instagram:

@rainbow_shaker where she shares her customers' projects and very useful tips

and

@thecolourfuldairy her new account where you can follow her journey to completely renovate an old dairy factory into a joyful home in East London