With so many colors available, it can be difficult to know which ones you should buy when you first start painting with acrylics. While we all know that it is possible to mix a rainbow of colors from just three primary colors (blue, red, and yellow), most of us don’t, preferring the ease of being able to squeeze a particular desired color directly from a tube; and some colors from the tube are simply brighter or darker than anything you can mix yourself. However, you can't buy or carry with you every color and tube of paint that's available, so knowing how to limit your color palette while still being able to mix the colors you want is an important skill.
While there are many limited color palettes you could use to start off painting with acrylics, the colors listed here make up a good basic palette of acrylic colors and from it, you should be able to mix all the colors you might want.
Get a tube of cadmium red medium (you also get a cadmium red light and dark). Cadmium red medium is a yellowish, warm red and relatively opaque.
Phthalo blue is an intense, extremely versatile blue. It gets very dark when combined with burnt umber and, because of its high tinting strength, only a little need be mixed with white to create lighter blues. (Also called phthalocyanine blue, monestial blue, and thalo blue.) It takes a bit of practice to use phthalo blue because of its high tinting strength, but many artists swear by it. If you find that you prefer to use phthalo blue more selectively, ultramarine blue is a good substitute and a very useful standard blue to have. Like phthalo blue, it is transparent, although the actual hue is different, and the tinting strength is high but not as high as phthalo blue.
Start with a tube of cadmium yellow medium. You can easily create a lighter yellow by adding white to this, though if you find you’re doing this regularly, consider buying a tube of cadmium yellow light too. Remember that if you want to darken yellow to try adding its complementary color, purple, rather than black, which tends to produce an olive green rather than deeper yellow.
Titanium white is an opaque, bright white with a strong tinting power (meaning a little goes a long way). Some manufacturers also sell a "mixing white", which is usually the cheapest and, as the name suggests, formulated to blend well with other colors.
Mars black is a relatively opaque color and should be added to other colors in small quantities until you’ve got used its strength. Another option is ivory black, but only if you’re not squeamish about it being made from charred bones (it was originally created from ivory).
Burnt umber is a warm chocolate brown that’s extremely versatile and likely to provide itself indispensable. It’s great for darkening the tone of other colors. Raw umber is very similar but slightly lighter and cooler.
Greens can be hard to mix consistently unless you’re meticulous to note the colors and proportions you used. Phthalo green is a bright bluish green. Mix it with cadmium yellow medium to get a variety of shades of greens.
Yes, you can make orange by mixing yellow and red, but if you’re mixing an orange often, you’ll save yourself time having it ready-made in a tube, so buy a tube of cadmium orange.
It is worth buying a very dark purple such as dioxazine purple since a pure purple can be very hard to mix, particularly using warm reds and blues.