gosh-i've been using dmc floss for 40+ years and have never had any bleed---do a color test- if it does bleed i simply would not use it-
the comment about vinegar----used to be the case-20 years ago---but the dyes used now days do not set with vinegar---the chemicals have been changed- the dyes that could be set with vinegar were acid dyes that are no longer used---due to safety - rule changes- so adding vinegar may freshen your fabric/act as a softener-but will have no effect at all on setting the color. you can use retayne, or rinse until no color comes off with color catchers---i've never known a need to pre-wash embroidery floss.