I don't pre-wash... Also, for what it's worth, Consumer Reports has demonstrated that those color catchers don't actually help prevent your fabric from picking up stray dye. The catchers turn color, but the fabric that is in there with the piece that is bleeding doesn't pick up any less dye than it would otherwise. You can see a video about it here:
https://www.consumerreports.org/vide...olor-catchers/