I've been calling these solid red kelpfish Gibbonsnia elegans or Spotted Kelpfish since frequently you only see one of the spots visible on the side. Now I found this one that has no spots at all. The Humann book suggests that coloration in G. montereyensis is highly variable with some individuals being uniform in color. In the meantime I'm paying close attention to each kelpfish I see, hoping to see one that I can conclusively identify as Gibbonsia elegans I think this one is probably Gibbonsia montereyensis.
Gibbonsia montereyensis