as long as the coloring was heat-set and treated properly they hold up quite well. we do coloring quilts at a local preschool every year and the first one a little boy i know still has his quilt he made in preschool 9 years ago...it is still holding up just fine...a couple of the pictures did fade some, he just got his crayons out and redid them but most have not faded hardly at all. the 2 that did were quite light to begin with. his quilt gets used and washed.
the only special treatment his mother has given the quilt is she does wash it in cold water..but then she tosses it into the dryer just like anything else a mother of 6 does. and we do not use any special crayons at the preschool, we use whatever crayons the child has...crayola and dollar store crayons work equally well. the key is using either PFD fabrics (prepared for dyeing) or pre-washing/preparing ourselves. for the preschool project i have been involved with for the past 9 years i have used PFD fabric. i iron freezer paper to the back, cut out 14" squares and give them to the kids..they color their pictures on the fabric squares. then i heat set them for them, using a brown paper bag and a hot iron. the brown paper collects the wax, the color sets into the fibers. then we get together and the kids decide on the fabrics for sashing strips and we work together to make it a quilt. we always combine the quilt project with other classroom activities..like working with shapes, we have used circles, triangles, diamonds, rectangles and squares. the teachers are very creative at combining activities with lessons, the kids learn lots. i set up a little sewing machine and they all work on their own quilts...the only things we do not let them do is iron/press. we draw lines on our fabric and they cut with their little safety shears, we draw lines for them to follow to sew, but if they make their seam 1" wide that is ok too...it is nothing but a very positive activity. as they get older we stress acurracy more but for the pre-schoolers it is more about the lessons being learned and creating something of their own, the technical part we do not stress over we do not want anyone feeling like theirs is not good enough. they are all good enough! and treasured. each child makes their own quilt to keep and each child makes a block for a class room quilt which the raffle to pay for their end of year field trip.