I suppose you could give all your squares a bath in a dish basin with warm water and a few drops of soap. Or place in small lingerie bags and use the washing machine.
But that is only if you want to, or there are certain red or purple fabrics that cause concern.
I am like you in that I used to wash all my fabric ten years ago up until about 2 years ago, but I don't do it now. I have my older washed fabrics that I still incorporate into quilts with my newer unwashed fabrics. I personally have not had any problems with shrinking or bleeding. I think that as long as you're not using fabric printed decades ago (which might be loosely woven or has unstable dyes), you will be fine as others have said by using a color catcher.