As a group, I find blues and yellows the most essential in my box. Interestingly greens are much further down on the list. As far as a single tube, Windsor blue and cadmium yellow medium. But I am also still mourning the absence of the color I most covet: the one I never found. When I was 10 years old I imagined finding a bucket of paint that was a color no one had ever seen. Still looking.
I guessed the cadmium yellow.
Me, I thought about this a lot, I would chose bronze yellow and paynes grey followed closely by raw umber and red oxide. Most of my paintings have the color pallete of a compost pile.
I love the idea of the "lost" color.