Lichen

Multicolored growth. I believe the yellow/orange stuff is Crustose lichen and the dark clumps on top are a type of moss. As with all Lichen, these are "composite organisms consisting of a symbiotic organism composed of a fungus (the mycobiont) with a photosynthetic partner (the photobiont or phycobiont), usually either a green alga (commonly Trebouxia) or cyanobacterium (commonly Nostoc)." - Wikipedia