I don't know about you but there are two way I pick yarn colors.
One is very visceral. I see a color and It's like a flood of emotion and desire to have that color. A deep bright blue that reminds me of the color of the morning sea on the beach in Belize. It's a green so perfect I can smell the pine tree and hear the birds chirping. The yellow of a crocus that makes you feel the crisp air and the crunch of spring frost under your feet.
My second method of choosing a coloway is to think functional. I'm spending a certain amount on yarn for a shawl I'd like to wear fairly often in my super air conditioned office and I mainly wear blue, black or brown to work, so it's got the match. Or I'd better choose a neutral color of this expensive yarn so I can get the most out of it.
So when my husband chose an amazing bright green and yellow colorway (Cherry tree Hill Supersock DK) for a pair of socks, I figured there was some interesting memory or sensory association for him. A vacation, a childhood place, perhaps. When asked the reason for his choice he replied "I wanted a bright color so I can find my socks lying on the floor in the mornings."