Q: We found on our deck banister a brightly-colored fungus. It is about 3/8-inch high. Are you able to identify it?
A: Wow….very cool!
It’s a myxomycete…one of the thousands of kinds of slime molds.
Your example is basically a big single cell with thousands of nuclei. They are formed when individual cells swarm together and fuse. The result is one large mass of cytoplasm with many nuclei.
It will dry out eventually and scatter spores which may land on other damp, organic surfaces as did yours.