Juvenile? About 1" long.
In the additional photos it is the larger, lighter one.
Body was darker than the usual sort, with a greenish cast. Tail had a lot of yellow. In the additional photos it is the smaller, darker one.
Under redwoods next to fallen log.
Lichen - On fallen redwood.
On the ground under redwoods. White underside.
Thinking some sort of puffball...?
With fruiting bodies.