I use the Ultra Clean markers to mark my quilt. I don't have any issue with washing them out -- usually I soak them in the tub with cool water for 20-30 minutes. Most of the colors come out that way. If there are any stubborn areas (and sometimes the reds will temporarily bleed onto nearby areas of the fabric), then I take a soft sponge with a bit of Tide Clear or Woolite & rub the fabric a couple times. Then I drain the water & run fresh water. 10-15 minutes later, all the color is out.
I do know other members have said that on occasion there will be a particular fabric that retains one or more of the colors. I always do a quick test before starting to mark with the Ultra Clean markers (or any markers, for that matter b/c some people also complain about the little Blue fabric markers not coming out).
I know the Crayola site recommends using warm water to wash the markers out, but I only use cool to cold temp water. Maybe try soaking the quilt for a longer time & rub a bit with a sponge & laundry soap (that always does the trick for me!). If that still doesn't work, you could try washing in the machine with warm water like the instructions say and see if that works. Good luck!