Subject to change if these materials look like crap, but here is what I'm thinking to replace the cobble with on the larger planets:
Light Gray Wool, ~650
Brown Wool, ~400
Orange Wool, ~ 650
Yellow Wool, ~300
Light Gray Wool, ~200
SATURN'S RINGS (*)
Cyan Wool, ~250
Blue Wool, ~250
(*) For Saturn's rings, my wife is pushing for a more stylized vision, using materials like Purple Wool and Orange Wool, instead of trying to use realistic tones. I'm considering this, so this material list may change.
There are chests for contributions in my room at the SGU commune, and I will update the signs to match this list. I will also eventually place donation chests on an observation platform near the planet build site, but the observation platform is not built yet.
I know this will take a while (and a lot of sheep), but I appreciate any help at all. Thanks!