Once it comes clean, it is good to go without further treatment.
I love basic Dawn detergent. Along with WD40 and duct tape, I think you can survive just about anything. I'm also a fan of heat treating running dyes -- thoroughly wet and soak, put in a safe for microwave pyrex type bowl, cover with plastic wrap and nuke it. Or you can boil on top of the stove.
I had one really bad experience with a Maroon fabric that completely ruined a quilt. I had prewashed it without a color catcher and thought I was good to go. That piece never stopped bleeding.
The darker fabric is a remnant of what ruined the quilt and has been washed at least twice. The other is from the same line/it started the same color -- I used the blue in the quilt with no problems and has been treated and washed at least 7 times and still runs like a thief in the night...