What Is Butterfly Pea Gin? (And Why It Changes Colour)

If you've ever poured a gin and watched it transform from deep purple-black to vivid violet right in the glass, you've experienced butterfly pea flower gin. It's one of the most visually striking moments in cocktail-making — and it's entirely natural.

At Twin Bridges Distillery, our Downstream After Dark is built around this magical botanical. It's our most celebrated spirit, a multiple award winner, and — hands down — our most Instagrammable product. But the real story isn't just the colour. It's the chemistry.

What Is Butterfly Pea Flower?

Butterfly pea flower (Clitoria ternatea) is a vivid blue tropical flower native to Southeast Asia. It's been used in traditional cooking and herbal medicine for centuries — most famously in Thai blue rice and colour-changing lemonades. The flower is naturally rich in anthocyanins, the same pigment compounds found in blueberries and red cabbage, which give it its deep indigo hue.

When infused into gin during distillation, butterfly pea flower imparts that signature deep blue-purple colour. The magic begins when the liquid meets an acid — tonic water, citrus juice, or even a squeeze of lime — and the pH drops.

Why Does the Colour Change?

Anthocyanins are pH-sensitive pigments. In a neutral or alkaline environment, they appear deep blue or purple. Add an acid — and the pH drops — and they shift to pink or violet. This is a completely natural chemical reaction, with no artificial dyes or additives involved.

In the case of Downstream After Dark, the gin sits in the bottle as a deep, mysterious purple-black. Pour it into a glass with tonic water and watch it bloom into vibrant violet. Add a squeeze of lemon, and it shifts again — brighter, more pink. Every serve is slightly different, depending on how much acid you add.

3 Cocktails to Show Off Your Downstream After Dark

1. The Classic Colour-Change G&T

The simplest way to experience the transformation. Fill a copa glass with ice. Pour 45ml of Downstream After Dark over the ice (watch the colour deepen as it chills). Slowly pour 150ml of premium tonic water over the back of a spoon — and watch it bloom. Garnish with a slice of lemon or a twist of grapefruit peel.

2. After Dark Spritz

A lighter, more effervescent take. Combine 30ml Downstream After Dark, 30ml elderflower liqueur, and a squeeze of fresh lemon juice in a wine glass over ice. Top with 90ml of chilled prosecco and a splash of soda water. The lemon juice triggers an immediate colour shift — your guests will be impressed before they've even tasted it. Garnish with a sprig of fresh mint.

3. The Murray Sunset

A layered cocktail inspired by sunsets over the Murray River. In a highball glass, add ice and pour 45ml of Downstream After Dark. Gently add 30ml of fresh orange juice (don't stir — let it layer). Top with tonic water. The three-layer effect — deep purple at the base, shifting to violet, with orange at the top — looks spectacular and tastes even better.

Where to Buy Downstream After Dark

Downstream After Dark is available online through our website with Australia-wide delivery. It's also available at select stockists in South Australia — check our stockist page or get in touch for your nearest location. It makes a genuinely unforgettable gift for gin lovers, and we offer it as part of our gift sets if you'd like to include it alongside other Twin Bridges spirits.

Distilled in small batches at our family-run distillery in Murray Bridge, South Australia — every bottle is made with care, and it shows.