I use a limited palette of only 3 colors and white. When I first began using these on the recommendation of my mentor, it was to learn to mix color consistently each time. After mixing the same pile hundreds of times using only those few options, you can learn how to get very accurate color matching. You never wonder which yellow you mixed with which violet to get that particular shade of olive. So, I set out to use this color palette for one year. I have never switched from it since, and it is the palette I use both in the studio and en plein air. (Incidentally, it is also the palette my mentor uses every day and has for 20+ years). What I have found during this adventure of learning to mix accurately and consistently, is that I can mix ALMOST any color with these few choices. I can mix umber or ochre or whatever, and you cannot tell it from the tubed version. So for me, it is simplicity now. It's not that I couldn't add those tubes of color in order to not have to mix them. Instead, it is that when I go out to paint or need to pick up a color from the supply store, there's not a lot of question what to throw in the bag. This also makes my plein air gear very lightweight!
When I began teaching using this palette, I wanted proof to support my words so I made several color charts. (More on that in the next entry). Even I was amazed! I knew I mixed those hundreds of great colors, but when you see them all laying out nicely in order, it's pretty incredible. When I lay the colors out on my palette, I always lay them out in order of the spectrum, and mix secondaries (USING THE SAME THREE TUBES) to lay between the primaries.
So my palette looks like this:
TITANIUM WHITE, CAD YELL MED, ORANGE, PYROL RED, VIOLET--ULTRAMARINE BLUE, GREEN, Mud from previous day's palette.