The blue color of this tea comes from a natural pigment called anthocyanin, which is found in many other blue or purple plants, such as blueberries and red cabbage. Anthocyanins are pH-sensitive, meaning their color can change depending on the acidity or alkalinity of the solution they're in. In the case of this tea, the anthocyanins are blue when the tea is acidic, and they turn purple or pink when the tea becomes alkaline.

This is why the blue flower tea changes color when you add lemon or lime juice to it. The citrus juice is acidic, so it causes the anthocyanins in the tea to turn blue. When you add baking soda, which is alkaline, it causes the anthocyanins to turn purple or pink.

The color change of this tea is a fun and easy way to demonstrate how pH can affect the color of natural pigments. It's also a great way to learn more about the chemistry behind the colors we see in nature.