I’m purely thinking out loud BUT – is there any footage of the background without the dancer? If you captured a still, you could then use that as mask to leave you with just the dancer; to which you can filter as you wish? You could then add that back to your still though I accept he wouldn’t cast a shadow etc. if that matters. If you’ve several clips of 20s, you really don’t want to be tracking over 1000 frames.
Alternatively – if you have successfully masked him in Color; you CAN do a bad TV style by adding a number of different filters; have a look around.