Depending on your level of skill, you can use a number of colors to paint tigers. Young artists and beginners usually start with premixed colors while more experienced artists blend their own. Both of these styles can achieve beautiful effects. Other interesting options include the coloring of rare types of tigers and colors you can use to make imaginary tigers, such as the bright ones popularized by the Lisa Frank brand of stickers.
The Basics
The most basic colors used to paint tigers with no color blending are orange, brown, black and an eye color -- usually green. These colors are the most comfortable for beginners to use and even experienced artists use them for the graphic "pop art" style effect they create.
Advanced
The advanced eye will know that tigers are not just orange, black and brown. Each tiny hair is a different shade that blends with the others to create the color we call "orange." More expert painters, particularly those who want a more realistic look, will generally blend their own colors to match a photo of a tiger. Hundreds of potential colors are created when mixing paints, so it is impossible to give a definitive list, but some common mixing colors include cadmium red, burnt sienna, raw umber, mars black, titanium white and a variety of colors for the eyes. These colors can be mixed in different ways to create infinite variations in color.
Rare or Unique Coloring
People love an albino tiger, but these animals are very rare, as are other colors and patterns caused by genetic mutations. In the wild, these mutations are more likely to get the tiger killed, so if you happen to see one or get a picture of one, take advantage of the situation. Mutation in the pigment genes allows for unpredictable effects, but generally the colors stay within the same shade family as normal coloration. You will never see a real purple tiger, for example, but you can definitely see white, gray, black, brown and pure orange ones. The stripes can be nonexistent, they can look more like spots, or they may even have the colors inverted -- a dark body with orange stripes.
Imaginary
If you want to paint a magical tiger unlike any real one, there is really no limit to what colors you can use. Purple, pink, green, blue -- the choice is up to you. You don't even have to add stripes or spots, if you prefer not to.