Fortunately, there are items you probably already have on hand that can prevent fabric from fading in the wash. An article from Lindsay Conner gives a good overview of what works and how to use it. You’ll find additional tips in the comments section below the article.
“Rainbow Bargello” quilt. It’s available as a kit here while supplies last.
In fact, if you don’t prewash your fabric, it’s a good idea to use this tip from the article to further set the dye and prevent bleeding:
“Prior to a first washing, you can also soak dark fabrics for 30 minutes in water mixed with ½ cup of vinegar and 2 teaspoons of salt to help set the dyes.”
Another good option for setting the dye during the first washing is to use Retayne (found here). (It’s also a good idea to add Color catchers to the wash to help keep bleeding dye from damaging your quilt. Synthrapol can usually remove dye that has bled into other areas of a quilt and further set remaining dye.)
You’ll find more information about retaining color when laundering in this article from Organic Authority.