My front signals are yellow and faded so I decided to spend my day off giving them a bit of a refurb before I shell out for a new set.
I went down to the local hardware store and picked up some sand paper. I went with a 600 grit and a 1200 grit. I had originally planned to also use a 2000 grit but they didn't have any. I sanded until the dust turned from yellow to white with the 600 and then used the 1200 to smooth it out. Finally I used some car polish I had lying around to finish it off.
I'm pretty happy with the result for $3 worth of sandpaper and some elbow grease!