I started trying to lean them toward the joke DWK made which was pretty much the joke made in the episode where spike's head apparently is what his cutie mark looks like.
"You're both purple unicorn with sparkly stuff on your plots"
But "purple" is a variant of *red* and BLUE is a primary color that very much stands apart from red
Inverting the image just gives us the Daring-Dont recolor of Glimmypoo.
