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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)

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  • $\begingroup$ After adding baking soda, I guess? Juice is acidic, but if enough base is added it may act as pH indicator and change color. $\endgroup$ – Mithoron Aug 8 '18 at 17:37
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    $\begingroup$ 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! $\endgroup$ – DrMoishe Pippik Aug 8 '18 at 18:29
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Cherries, like red cabbage, hibiscus and many red or purple colored fruits, contain a class of compounds called anthocyanins of general formula:

enter image description here

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.

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