Why Unicorns Are White. And A Corollary.

(Or at least, why pretend unicorns are always white.)

"Because unicorns eat cucumbers.
Inside cucumbers it is white.
The white explodes out to their skin."

Hmmm, OK, I follow that.
But what about the skin of the cucumber? That's not white.

"Well... the green is the unicorn poo."

Oh.