Color Picking - Play By The Numbers
Doing some refresher research on color theory today ... sometimes I really regret selling back my college books. A base color selection can be completely subjective, but the accompanying and contrasting colors are not random. Humans react to color combinations based on cultural cues (red+green=Christmas, etc), and *mathematical calculations*.
This is one of the hardest concepts to teach new designers who want to randomly pick colors because they "look good".
Color theory isn't new. Although they couldn't articulate the concept, the master painters unknowingly mixed pallets of oil and pigment into specific schemes that can be backed up by numeric color theory today.
Back in the day, we did these calculations on a (gasp) calculator -- nowadays scheme applications do all the math for us. Adobe's is a good example: http://kuler.adobe.com/#create/fromacolor