Being a replication, Dark Keroro resembles his original, with some differences. His natural skin color is dark green and his lesser skin color is pure black. His pupils are red and his hat is gray. His hat star symbol is also pure black. There are black stripes under his eyes. He wears a torn red cape. Dark Keroro is a much more "improved" Keroro. He is a much smarter and more serious invader then Keroro, and successfully dominates Pekopon in 2 minutes, using a mind controlling device. He is equipped with a massive, much more improved version of the Keroro Robo. He commands a gigantic spaceship with an anti-barrier that enshadows Inner Tokyo.

[From: Keroro Wiki]