Eldargal, i didn't know you was that way inclined! (This is a joke before I get flamed).
Ultramarines. Maybe more of a reference, but the 's' makes it a pun?? Ultramarine is a standard artists colour (GW Ultramarine blue, maybe very slightly darker). GW simply named their chapter after the colour they were painted. Quite a good one as it already included the word marine.
No one would take me up on a chapter of Cerulions