Tan is an easy colour to create. It is also extremely useful. Often, neutral colours in painting are not sufficiently appreciated. The less showy neutrals provide a counterbalance for more dynamic colours. In addition, the can produce a neutral ground to which almost any colour can be successfully added. The paucity of hue in neutrals is what makes this possible. Depending on the type of tan you want, there are corresponding artist's colours to achieve tans that go from yellowish to reddish, or a solid tan.
Mix a teaspoon of white paint with equal parts of burnt sienna and yellow ochre. The volume of the burnt sienna and the yellow ochre should be about equal to a split pea. This is because their pigments are stronger, and tan is on the light side. Mix the colours on the palette. Sweep them about with the palette knife. Mix until you have a solid colour. For lighter tan, add more white. For darker tan, add more yellow ochre and burnt sienna in equal parts. This combination produces a typical tan, without leaning towards red or yellow.
Mix a teaspoon of white paint with burnt sienna, in about the volume of split pea, on your palette. Again, mix well. This produces a reddish tan. Adjust with burnt sienna and white as required to reach your desired tone. Make sure the colour is solid.
Mix a teaspoon of white paint with yellow ochre for a more yellowish tan. Use about the volume of a split pea of yellow ochre. Adjust as necessary. You can even add a hint of burnt sienna if the tan appears to yellowish. Blend the paint well. Scoop and turn over the paint periodically on the palette to ensure full mixing.