The existing Martian Coasters (including the promo coaster) are all white, each with a primary color (for the squares) from the Rainbow Treehouse set, and accents from the Xeno Treehouse set (with grey replacing clear). Everything is outlined in black How about a second Martian Coaster set: a base color of black, with the primary color for the squares being the Xeno colors, and the accents being the Rainbow colors, all outlined in white? (The matching Promo coaster, perhaps issued on the anniversary date of the release of Treehouse, would naturally be black, with grey squares and black accents.) (I'd buy a set, no question.) (I wish I had the time and ability to actually demo Treehouse and/or other LL games so that I could earn some Rabbit points and get a Grey stash!)