Back in the days of frigates and pirates, to show your colors meant to lower the flag you sailed under and then raise the Jolly Roger to reveal that you are, in fact, pirates.
Which is kinda strange, considering that the Jolly Roger was a white skull on a black field. Not very colorful at all.
I’m sure you could make a comment about rainbow flags and “butt pirates” but that’s highly offensive, and you should never use that kind of language.
Instead, just say “Yarrr!” and “Shiver me timbers!” over and over.
Otherwise, you should prepare to be boarded.