depends on the scuff ! And the colour of the gelcoat. never heard of a coloured polish i m afraid. If you can feel it with your fingers, you have some work to do. You could try wet and dry, start at 1600-if thats too fine, try 1200 etc. What you dont want to do is start too low a grit or you will just add more scratches that are a pig to get out. But to get a shine you ll need some rubbing cmpound and some sort of polisher.
Ive got areas with lots of small scratches on my recently purchased Westerly (scratches are so small, they feel smooth & undetectable to the touch), a friend fixed it on his boat by lightly sanding with very very very fine sandpaper, although it took ages. A club member suggested rubbing compound (some posts recommend farecla). My surveyor suggested using bleach on it to clean out the little scratches - they become invisible. Lots of ideas, although I havnt got around to trying any of them yet!