Flesh tone is one of the most difficult color to mix. There are commerically available colors for it, but they tend to be too pinkish. I always mix my own flesh tones because I can have complete control, but it has taken me a very long time to know what I'm doing. Different techniques also call for different mixtures.

My goal in painting flesh is so that all the color makes gradual transitions over to another (just like a real human being), and prevent areas where you can tell immediately that a different color has been painted on.

A. Mixing flesh tones - I mix 3 different colors for fleshtones: basic, highest highlight and deepest shadow colors.over the Here are some receipes that I have used before:

• With artist acrylics, the David Fisher formula is burnt sienna, raw sienna and titanium white, about 1:2:4 in his video. I found his mixture too red and dark, and 1:3:6 is about right for figures of real people but still too dark for anime figures. I use this mixture for doing shadows for anime figures. For anime basic flesh tone I mix apricot (a pinkish fleshtone), white and yellow ochre, approximately 1:4:1, if the mixture is too pink cadmium yellow medium is added. For highlights, more white and a little bit of cadmium yellow medium is added to the mixture.
• With model paints such as Mr.Color, I'm using Gunze yellow orange (#58) and red(#3) and sky blue(#34) and Mr. Base white to mix the flesh. The exact ratio again is eyeball, a start would be 8:1:1:a whole lot, but it depends on what you want to achieve. I tend to use a redder/pinker flesh for anime characters and a darker/bluer mixture for life subjects. Gunze's red is very strong so it should be added very carefully (or use pink). I actually mix big pots of flesh tones by adding colors to a jar of Mr. Base White. For the shadow color I mix to the original flesh pot red brown (#?) and more yellow orange to cancel out the red.
  
  Try to mix & paint skin tone in broad daylight. Under artificial lighting, the mixture will come out with a wrong color (even with color-corrected lightbulbs), and your shading will be off because artificial light sources tends to cause less contrast than it actually is.
  
  Disclaimer: The ratios and colors are just for reference only. It really helps if you get a picture of the skin tone you want and mix according to it. Also I have different fleshtones for my figures at different times, and I'm still experimenting with various mixtures.
  

Approach 1: using the basic flesh tone I airbrush in all areas, more colors for shadow areas and less for highlights. Then grab the shadow flesh tone and airbrush in the shadow areas. Then I lightly mist the basic flesh tone over the shadow to blend in the shadow colors. I only do this when I think the shadow looks too dark and out of place. Then airbrush in highlight fleshtone for the highlights. It helps to locate these areas if you study pictures of people, and know the stop-sign rule (from Shep Paine's scale figure book) of how lighting interacts with colors. Finally, I've heard good things about Badger freak-flex premixed flesh colors but haven't tried it, you can read more about it from Jerry's page.

Approach 2: The problem with the method above is if you screw up (which happens to me often), fixing is not trivial because you cannot cover up your mistake. When you airbrush, the underlying color will show through the top color giving a sense of transparency. But to re-achieve this effect after a screw up tends to be very difficult. So what I do now is to airbursh the base flesh tone all over and make sure it uniformlly and opaquely covers the entire kit. This way, when you screwed up you can wipe out the mistake with the basic fleshtone and redo the area. Then I do the shadows and highlights as usual. I use very thin paints for shadows and highlights so that I can achieve a lot of gradation. Low pressure (~5psi) and thin paint allows you to draw very fine lines. I also generate more contrast than needed at this point. Finally I bind all the colors together. At this point you can decide whether you want a light or dark overall fleshtone by misting a mixture of the basic and shadow fleshtone. I keep on misting until there are no drastic transitions in color on the kit, which I consider very important in female skin color.

Skintone Colors: I usually use only titanium white (highlights), mars brown (shadow), naples yellow light (basic flesh tone), burnt umber (deep shadow), yellow ochre (mix with shadow colors to "smooth" out the color), napthol red (blushes, lips)
Mixing: I use naples yellow light as the basic flesh tone, mix in titanium white for high highlights and mars brown for deep shadows. I also sometimes use burnt umber in place of mars brown for very natural shadows. For blushes a mixture of red, white and naples yellow light is used; some mars brown are added for a deeper red.