Boat is white gel coat and either at the marina or the shop that fixed my skeg the white gel deck got black paint specs on it.

How can I remove this?

acetone, maybe just buff it off

If nothing else, Wet sand it with a fine paper like 1000 grit and then buff it and wax it

Laquer Thinner. Wipe it with a laquer thinner wetted rag, then follow while its still wet with a dry rag.

Clay bar works too.