Not really practially possible, but doable would be to use a flourescent ink and blink a blacklight ype lamp.

I have no chemicals in mind nor do I know if the process is possible but the way it might work is a dye that reacts to light by fading (which many dyes now do slowly) and the fading is a chemical reaction that changes the chemistry so that, at a certain level a secondary process would take over and would reverse and recreate the original dye. The energy for this cyclic reaction could come from the light itself. Therefore, the brighter the light, the faster the blink. This could be a very useful process for gauging the brightnss of the illumination. If it were possible. Again, if this could be managed, a double image could be managed where two images alternated.

There is a blinking-ink.co.uk