If you are trying to replicate the color of human skin when decorating a cake, cupcake or any other food product, the accuracy of the color will be a crucial factor in the outcome. Flesh-colored food coloring exists pre-mixed and available for purchase, and will yield the most accurate results. But if you're in a pinch, you can create a similar tone from the colors you already have in your cupboard.
Create brown food coloring by mixing equal parts red and green food coloring in a small bowl. Test the color by inserting a toothpick into the mixture and mixing it into a spoonful of white icing. Add a drop or two of yellow food coloring, if necessary.
Add several drops of red food coloring to another bowl. Add water and mix, until a light pink shade is achieved. Test the shade, as before.
Mix light pink food coloring with a small amount of brown food coloring in a third bowl. Start with conservative amounts of each, increasing as necessary, to create the shade of flesh desired.