After reading the post about the Plaza Yellow Cap being more valuable if not cracked I decided to try to dye one. Bought Ritz Golden Yellow 42 Dye. Used half the pack with one cup water. I was doubtful that it would work but to my suprise the results were amazing. I would be hard pressed to tell which was my original and which one was dyed except my original has a crack in it. I don't know if this would work on the blue but if I needed a blue I would certainly give it a try.