I had a flash of blinding inspiration when I was mixing the dye for the schools project. Paint the lids to match the contents! Makes the colours more easily identifiable and the chances of the right lids going back on the right bottle sightly greater (although I wouldn't like to give you odds).
When visiting the school recently I was looking at the last dyeing project completed about six months ago. This was disperse dye which I knew was light fugitive but, man, they're not kidding! If you click back to March you'll see the way it used to look. Sadly today it's washed out pastel.
Lesson learned. Disperse dye is not for posterity.