How many colors do you like to have in your palette? How many do you need? How would you decide which ones are your essentials?
Luckily, we don't often have to make decisions about which colors stay and which must go (only when some fool gives it to you as a homework assignment).
Many artists like to have a warm and a cool of each color family, which, theoretically, provides a great deal of versatility. For example, a yellow that tends toward orange (New Gamboge), and one that is leaning toward green (Aureoline). You may ask, " Why not just get a yellow that has neither red nor blue?" Why, indeed.
Some like to add potent dyes, like Pthalo blue and green, and a couple of Quinacridones, for when the color you're mixing needs a quick shot of warm or cool, or when you want a powerful dark. Please pass the Transparent Pyrol Orange!
There are lots of ways to fill your palette. I met a painter once at a workshop who had 5 palettes. She needed her own whole table. I have to admit I was a little jealous of the one devoted entirely to blues.
I think we may all be a little weird when it comes to color. Why is it, for example, that I usually have 5 blues, and I can tell you what they are without hesitation, but I only have two reds, and I'm never sure about their names? There's something to be said for just gathering the colors you simply like best, and watching to see if the need for additional colors arises.
For homework, let's do some painting with a limited palette. Here are a couple of popular sets that have passed the test of time:
Yellow Ochre, Cadmium Red Medium, Ivory Black plus White. Some lists add Vermillion, Viridian, and/or Cerulean Blue.
John Singer Sargent:
Raw Siena, Burnt Siena, French Ultramarine, Ivory Black. Traces of Cobalt Violet and Prussian Blue
Choose your own group of colors, or try one of these. Limit your array to 4 or 5 colors. Maybe 3, if you're feeling brave. Some of the mixes you make will probably be less than perfect matches. Rather than add more colors, try letting them be to find out how the whole painting is affected by the limited palette. Give it a chance to assert its cohesiveness.
Please search for your own image, and bring it in so we can see how the palette you create works.