I came up with a chapter of dark blue colored space marines with alligator theme who are bestest and everything and can totally beat your chapter and love wearing albino alligator skins. Their favorite tactic is massive "death roll" drop pod assault at enemy's weakest point. They are based on post-apocalyptic full-night ex-hive bayo world and have "corax" genesed with a quirk that makes them constantly stream tears aka "crocodile" tears. I've yet to come up with a cool name for them: Primal Bortherhood? Blue Reptiles?