# What happened when the cherry juice turned blue?

When I was eating cherries today, some of its juice spilled on my shirt. Attempting to clean it, I poured a solution (baking soda, vinegar, toothpaste, and salt) onto the fabric. Though it did not remove the stain, the colour turned from a wine red to a subtle blue.

So the Question is: Why did it happen?

(This is not that technical so I'm not sure how to classify it)

• After adding baking soda, I guess? Juice is acidic, but if enough base is added it may act as pH indicator and change color. – Mithoron Aug 8 '18 at 17:37
• There are many naturally occurring pH indicators. See en.wikipedia.org/wiki/… . BTW, red cabbage goes through the whole spectrum from very acid to alkaline! – DrMoishe Pippik Aug 8 '18 at 18:29

where $\ce{R_x}$ is either $\ce{OH}$, $\ce{OR}$ or $\ce{H}$. In basic medium it loses a proton and it converts to a non charged chinone like structure, which has a blue color.