Here is a cute coloring bag I made for my little niece! There is a pattern from Clothesline Quilts, which I used and then modified to fit the larger crayons. It was easy to make and fun and my niece LOVED it! She even slept with it the first couple of nights.
Clothesline Quilts also sells finished crayon bags for $15-$25. Check them out here!
Have fun sewing (or purchasing) a coloring bag for your kidlets!