It's even better to soak them in hot water with Retayne added. I do this for all my red, dk blue, dk purples, etc., etc. Retayne is made specifically to make dye permanent and will stop the bleeding. It's best used before you cut your fabric.
After you use the bleeding fabric in a quilt, it's best to use Synthrapol. It is made for dyed fabrics that have already bled and the fugitive dye has deposited onto nearby fabric. It is a product made to keep dye from settling back on fabrics.