Yes, the Pot Pourri Socks I knit in Claudia Hand Painted Yarns in fingering weight lost a lot of colour in the washing machine. I washed them in 40 Degrees Celsius. Normally I'd be upset with the loss of colour, but this time I danced (or considering my hips; treid to dance) a happy dance around the house before pinning them to dry outside.
When knitting them, I was a bit dissappointed that they turned out to be so dark and boring... Now they're much better! Almost perfect...