I have had some problems, particularly with red fabrics, but also with many others. The reds will bleed! I always treat my vibrantly-colored fabrics with a laundry treatment product which "sets" the dye. I have had deep blues bleed. If you don't pre-wash your fabric, at least test a small strip of it in a glass of hottest tap water available. If it's going to bleed, it will and you can tell by dipping a white paper towel into that same glass of hot water. The bleeding becomes more visible on a white paper towel. As I've also said many times, DISCRETION IS THE BETTER PART OF VALOR! I also use color catchers in the wash, even if I've previously treated the fabric used in the quilt. I'm operating here on a very strict budget and cannot afford to ruin a quilt by not protecting it against bleeding. I also pre-wash all my fabric, which isn't hard because I don't do quilts to sell and I don't have a large stash. So, first I test every fabric for bleeding, then, I serge across the cut ends to prevent raveling in the wash. If the fabric bleeds, I treat it with the laundry treatment product I've found works every time. Otherwise, I just launder the fabric, dry it and iron it (if it's badly wrinkled), fold it and add it to my stash! Red fabric is particularly bad to bleed and I use a lot of red, so it gets tested for bleeding first. But, bleeding is a problem possible in every color in the rainbow.