Watercolors? Make it a large Palette.

For oil painters, the idea of limited palettes is well ingrained. All you need is a warm and cool of each of the primaries and a white and you are basically good to go. This is something artists who start out in oils tend to want to migrate with them to watercolors. You wouldn't think of it for pastels of course, but somehow watercolors are seen as closer to oils in a manner.

That is not exactly true. As a matter of fact there is more in common between pastels and oil paints than with oil paints and watercolors. Mostly pastels and oil paints are used in opaque applications, while watercolors are transparent.

That is the key. It is well known that the more you mix colors, the less vibrant and more muddy they become. In the case of transparent watercolors, I prefer no mixing on the palette at all. If any mixing needs to happen, it is better for that to happen on the paper so that their vibrancy remains intact. That is why I have an embarrassingly large color collection on my palette. I admit that I rarely use more than a few at a time, but I like to have them there ready for use any time I needed them.

The less one mixes watercolors the more these colors reward you in the end. I understand that many of the colors on my palette are not single pigment colors. Some are mixes in their own right, but a color-man's mixture in the milling or composing process is very different from an artist's mixture. One is calibrated and ends up in a consistent product, the other is done in the heat of the painting process.