Why Does Butterfly Pea Tea Change Color? The Science and a Recipe

Pour a squeeze of lemon into a glass of deep blue tea and, within seconds, it swirls into violet and then magenta. It looks like a magic trick, but the answer to why does butterfly pea tea change color is plain kitchen chemistry: the flower’s blue pigments are natural pH indicators. Acid shifts them toward purple and pink, while alkaline ingredients push them toward green.

Below you will find the science in plain English, a mixer-by-mixer color chart and a layered lemonade you can make in five minutes.

Key takeaways

• Butterfly pea flowers (Clitoria ternatea) get their color from anthocyanins, mainly delphinidin-based pigments.
• Anthocyanins change shape with pH, and each shape absorbs light differently, so the color you see changes.
• Acids such as lemon, lime and tonic water turn blue tea purple to pink; alkaline ingredients such as baking soda turn it green.
• Pure butterfly pea is a caffeine-free herbal infusion, but many blends (including ours) contain real tea and therefore some caffeine.

In this article

1. What is butterfly pea flower?
2. Why does butterfly pea tea change color?
3. Color chart: what each mixer does
4. Recipe: color-changing butterfly pea lemonade
5. Troubleshooting the color
6. FAQ

What is butterfly pea flower?

Butterfly pea, Clitoria ternatea, is a climbing vine in the legume family that thrives in warm, tropical climates. Its vivid blue flowers are dried and steeped to make a bright blue infusion. In Southeast Asia the flowers have long been used as a natural food color, for example to tint the rice in the Malaysian dish nasi kerabu, and today bakers and bartenders use the same blue for ice cream, bread and drinks.

On its own, the flower tastes mild: lightly earthy, a little woody, not much more. That is why most color-changing teas blend it with fruit, citrus or tea leaves for flavor, and why the color is the real star.

Why does butterfly pea tea change color?

The blue comes from anthocyanins, the same family of pigments that colors red cabbage, blueberries and purple grapes. In butterfly pea, delphinidin-based anthocyanins are the most important.

Anthocyanins are sensitive to pH, the measure of how acidic or alkaline a liquid is. When you add acid, hydrogen ions attach to the pigment molecules and change their structure. A molecule with a different structure absorbs a different part of the visible light spectrum, so it reflects a different color back to your eye. Add base instead and the opposite happens.

The short version

• Plain brew (around neutral): deep blue.
• A little acid: indigo to purple.
• More acid: magenta, fuchsia, then pink.
• Alkaline: teal, then green, and with strong bases eventually yellowish.

The change is gradual, which is the fun part: add lemon a few drops at a time and you can stop at any shade you like. If you like seeing pH at work in your cup, our article asking is coffee acidic? applies the same scale to coffee.

Why not every blue drink changes color

Only natural, pH-sensitive pigments do this. Drinks colored with synthetic blue dye will not budge when you add lemon. If your tea does not change at all, it may not contain butterfly pea, or there may not be enough pigment in the brew.

Color chart: what each mixer does

Baking soda gives the most dramatic green, but it tastes unpleasant, so keep it for a science demo with the kids rather than a drink.

Recipe: color-changing butterfly pea lemonade

This is the classic party trick: a blue tea layer floating on lemonade that turns purple as you stir. It works with any butterfly pea tea. Our Butterfly Blue blends organic butterfly pea flower with white tea (Bai Mu Dan), pineapple, peach and citrus notes, so it brings flavor as well as color.

Ingredients (makes 2 tall glasses)

• 2 teaspoons (about 4 g) Butterfly Blue or another butterfly pea tea
• 1 1/2 cups (360 ml) water at about 175°F (80°C)
• 1 cup (240 ml) lemonade, or 1/4 cup (60 ml) fresh lemon juice plus 3/4 cup (180 ml) cold water and 2 tablespoons (25 g) sugar or honey to taste
• Plenty of ice
• Lemon slices to serve

Steps

1. Steep the tea in the hot water for 3 to 4 minutes, which matches the brewing guide for Butterfly Blue (2 g per 12 oz cup at 175°F). Strain.
2. Let the tea cool, then chill it. Cold tea floats better on top of a sweetened layer.
3. Fill two glasses with ice and pour in the lemonade.
4. Slowly pour the blue tea over the back of a spoon so it sits on top of the lemonade.
5. Serve with a straw. Stir at the table and watch the blue turn violet and pink.

Tips and variations

• For sharper layers: sweeten the lemonade layer; sugar makes it denser, so the unsweetened tea floats on top.
• Sparkling version: swap the lemonade for tonic water and a squeeze of lime. Our espresso tonic uses the same mixer if you want a coffee version too.
• Caffeine-free version: Butterfly Blue contains white tea, so use pure dried butterfly pea flowers for a fully caffeine-free drink, or mix in our caffeine-free Hibiscus Berry Tea for a deep red layer.
• Hot version: serve the tea hot with a lemon wedge on the side, and let each guest change their own cup.
• Ice cubes: freeze the blue tea in ice cube trays and drop them into lemonade; they turn purple as they melt.

Troubleshooting the color

• Tea looks gray or murky: it may be oversteeped or brewed with very hard water. Try filtered water and a shorter steep.
• Tea is already purple before you add lemon: some blends contain citrus or other acidic ingredients that shift the color early. That is normal.
• Color is pale: use more tea, not a longer steep.
• Layers mix immediately: chill the tea first and pour more slowly over a spoon.
• Color fades after a day: anthocyanins are sensitive to light and heat. Keep brewed tea covered in the fridge and drink it within a day or two for the best color.

Butterfly pea tea FAQ

Why does butterfly pea tea turn purple with lemon?

Lemon juice is acidic. The acid changes the structure of the flower’s anthocyanin pigments, so they reflect purple and pink light instead of blue.

Does butterfly pea tea have caffeine?

Pure butterfly pea flower infusion is a caffeine-free herbal drink. Blends that include real tea, such as Butterfly Blue with white tea, contain some caffeine. For caffeine levels in tea, see coffee vs tea caffeine.

What does butterfly pea tea taste like?

On its own it is mild and slightly earthy. Most of the flavor in a cup comes from what it is blended with, such as fruit, citrus or tea leaves.

Can you make butterfly pea tea turn green?

Yes, with an alkaline ingredient such as a tiny pinch of baking soda. It makes a striking science demo, but it does not taste good.

Is the color change natural?

Yes. It is a natural pigment reacting to pH, the same chemistry that makes red cabbage juice a classic school pH indicator.

Sources

1. Butterfly Pea, Herb Society, South Texas Unit.
2. What Makes Butterfly Pea Flower Tea Change Color?, Chowhound.

Facts checked in October 2026.

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