I have started making homemade yogurt, and I usually keep two types at the same time. One is a lactobacillicus bulgaricus strain, the other is a bifidus strain. They taste differently and look exactly the same - so I usually want to know which one I am taking out of the fridge, but can't tell by looking. I make the yogurt in small jars meant for home canning, and they only come in a single color.
Unlike jam, the turnaround time is short, I only make 6 jars per batch of any type, and eat at least one of each type per day. So I want something which survives washing the jars (so not paper labels). I also don't want to make permanent marks on my jars. I have been thinking to start putting something foodsafe in each jar such that it is visible from the outside, but don't have ideas of what this thing should be.
Ideally, the solution should also work for glass clip-lid containers, like these, because I might switch to them:
What is a practical and aesthetically pleasing solution for distinguishing the yogurt types?