unless there is a worry about color running usually pre-cuts are not meant to be pre-washed. the manufacturers say it is not so necessary as it used to be. if you are worried about color runs i would test them in the sink. if they do need to be pre-washed use the net bag. any time i pre-wash i put in washer and dryer, there are only 2 reasons for me to pre-wash, color running or shrinkage. if i'm worried about shrinkage it is necessary to put it into the dryer...so the shrinkage gets done. i would think pastels would be stable.