I'd let it go, be delighted with the quilt, enjoy giving it in this more pristine/new-looking condition, and tell their mother that either you would like to wash the quilt the first time it needs it, or write down instructions for her on how to wash it in the way you would have, giving HER the product. Then I'd think about how the quilt will probably mean most after it's been washed 5 times anyway, and this will likely be the least important thing EVER in the long run!
But then, of course I'm not seeing what you're seeing, Harmony, so if you feel you should go ahead and wash in - I can't remember the name but you'll find it - then do that with a happy heart. It's all good. It will be softer and cozier, which is not a bad thing. So impressed with you for making this gorgeous quilt.
Maybe when you buy solids in the future you should question the shop about whether any of their brands have any promises about color not running, or if they would recommend some that never run, etc. I just can't help but think this is not YOUR fault but the fault of manufacturing. I guess I'm thinking, what if you bought downright expensive fabric in order to avoid this situation. If it would work, it would be worth it.
No you certainly shouldn't have to go over to pastels! Having contrast in a quilt is very important - that's how we see the patterns and the eye is drawn to different parts of the quilt. So you are NOT wrong to use brights or darks. You are following in the footsteps of every other quilter. If a fabric can't keep up with that, it's certainly not your fault.