Foil

the rainbow is in the angle, not the ink.

a holographic die-cut sticker: tilt it toward your finger and the colour runs, because it was never on it

A holographic sticker has no printed rainbow: the foil is layers thinner than a wavelength, and its color is light that survives bouncing between them, depending on the angle. Tilt it and a different color survives.

Concepts: color, light.

An interactive you play with one thumb, on Wundr.