I can only assume, given the fact that I am the only person who sees Frank change colors, that I have been chosen as Frank's prophet. As the prophet of Frank, it is my obligation to discern His will, and convey His commandments to the world. So far, this is all I've been able to come up with:
I am Frank thy goat. Thou shalt have no other goats before me!
Yes, I know, it is rather derivative, but it is the only thing I can think of. Maybe there will be more later, and maybe there won't. I only said I was a prophet, after all. I didn't say that I would be good at it.