My personal technique, when I do wash fabric, is to wash each fabric separately in the sink (unless we are talking yards and yards, in which case, I throw that into the machine on extra low, together with a white wash cloth. That way, I can tell which fabrics are running, if any. If one does run, then I will either soak in white vinegar, or possibly use some retayne, or, depending on how important keeping the color intense is to me, I might just rinse until the water runs clear.
If you are using premium quilting fabrics, the chances of running and significant shrinking are low, and more and more quilters are skipping that step. If however, you are using a mixture of lines and qualities, or some of your fabrics are older, then washing is a good idea. And reds are notorious for running, so I will often wash them, specially if there are light fabrics in the finished project.
RST