Yes, that’s right, if you take the colour out of some foods, they react with acids and alkalis to give different colours – so you could easily test substances at home to see if they are acidic or alkaline.
All you need to do is extract the colour by grinding the skins or pulp in some warm water. That’s it (it can be a little messy so be warned if you want to try this at home!). Deep coloured foods like red cabbage, blueberries, red radishes, and plum skins work well.
Maybe try some different ones yourselves?
Chemistry Teacher / Form Tutor for Year 12 Calypso