I was mounting some samples into my foldscope with some colored paper-tape just the other day, and the most interesting part of the sample turned out to be the tape itself.  This is just standard colored tape, often used in many laboratories for labeling bottles and things.

When I looked at the tape, I noticed that the colors are actually pigmented rather than dyed.  Perhaps this is why this paper tape is always so expensive!  It’s quite good quality material, and the color never fades or transfers.

Here’s a view of what this tape looks like on the human-eye scale: