Lenzites betulinus

Scientific name:   Lenzites betulinus (L.) Fr.
Derivation of name:   Lenzites is named for the mycologist
H. O. Lenz; betulinus means "inhabiting birch trees" although
birch (Betula) is only one of many tree genera occurring as
a substrate.
Synonymy:   Daedalea betulina Fr.; Trametes betulina (L.)
Pilat
Common names:   Multicolor gill polypore.
Phylum:   Basidiomycota
Order:   Polyporales
Family:   Polyporaceae
Occurrence on wood substrate:  Saprobic; solitary or
grouped on dead deciduous and conifer wood; July through
December. 
Dimensions:  Caps 3-10 cm wide.   
Upper surface:  Covered with coarse hairs; concentrically
zoned with various colors, older specimens sometimes tinted
green with algae.
Pore surface: White to creamy-white; gill-like.
Comments: The gills are tough and leathery, unlike the gills
of the true gilled mushrooms. The pores of this poroid fungus
develop into gill-like structures.

More information at MushroomExpert.com:   

Figure 1. Lenzites betulinus on a dead branch.
Photo © Gary Emberger.

Figure 2. Zonate specimens but not particularly colorful.
Photo © Gary Emberger.

Figure 3. An amazingly colorful specimen!
Photo © George Morrison.

Figure 4. Colorful concentric zonation with a little green
thrown in (from the growth of algae) for good measure.
Photo © Gary Emberger.

Figure 5. Turning over a cap reveals the distinctive
gill-like structures of this species.
Photo © Gary Emberger.

Figure 6. A close-up of the gills. Photo © Tom Volk.