Skin tones can be a challenge. Here’s a couple of articles to simplify the task of making people look less alien-like.

Photoshop Color Skin Tones Tutorial
For those interested in coloring graphically upon the computer, painting, pastels, colored pencils, markers, and any other coloring tool, skin tones are necessary part of human color. The worls is full of variety in color, including the human skin. I look around, and I see many people getting the skin colors wrong. It can be too yellow, too pink, or just not the right color. Getting a realistic skin tone can be a really tricky business, but, there is an easy solution to this dilemma. I created this tutorial for Photoshop on Photoshop 7. I’m not sure what else will be compatible before Photoshop 7, or other products, but I would think that the steps would be similar.

Here’s another short tutorial.