NileBlue

NilePurple

Gemini, links to https://www.sciencedirect.com/science/article/abs/pii/S10759... that says that bacteria split the tartrazine in your guts, so I guess no.

Also as the main article explain, to get the effect the concentration must be quite high, like a 5% solution for 12 hours. That's like 50x the concentration of tartrazine in fake orange juice, that is probably dangerous to drink or take a bath.

I wonder if this could be applied to living tissue.

That's not a joke. Not only a cool party trick, but could help in diagnosing some medical conditions.

I tried to take a look. They have to match a refraction index of lipids of 1.43-1.53. A sugar solution from 0% to 80% has an index of 1.33 to 1.44 so it's too low. And 80% solution of sugar is a lot, they are using a 5% solution of tartrazine (that is also a lot, but a smaller lot).