I have a friend who quilts about 30 quilts a month for charity. She uses blue almost exclusively, she says it blends with almost every quilt. However, most of the quilts she gets are scrappy. I agree with stocking up on neutrals.
Once you get the tension set perfectly in your longarm, I'd recommend either you stick with that brand/kind/weight of thread, or write down the tension settings that work with that thread. If you go from using Glide to King Tut, you will most likely discover you'll have to adjust the tension.