Have you ever thought about uncommon pairs of color? Something about two unlikely shades side-by-side draws your attention? I never thought much about that until these last few years when I started to draw and paint a lot and when I learned to knit. Certain colors stand out more together than they do alone, I've noted.
I also think about combinations from the past. When I was a teenager, my mother bought me a long-sleeved blouse, a print with dark, goldish-brown patterns on purple fabric. Many times, sitting in a class with my arm resting on the desk, or at a dining table, I stared at that fabric, and that paired combination of colors is imbedded in me. Another memorable fabric decades back had a background shade of cream, with purple and green vines and flowers - a dress I wanted but didn't buy and have never forgotten. Orange and gray originally caught my attention on a bakery counter, and this showed up in my drawings for some time. Pink and gray - when I was a kid, we played The Game of Life and I'm still fascinated by the gray plastic car carrying pink pegs (representing babies born in the game of life). Pale yellow and gray have a pleasing gentleness. Sometimes when I am knitting, two skeins that I think have no compatibility look bright and inseparable sitting side by side near the chair. Knitting those colors together is a happy adventure.
It's not just about the colors though; it's about how those colors are intercepted by the observer, like the third corner of a triangle.