Part of the reason the cards are so eye-appealing is that the artists were masters of teasing the appearance of many, many hues out of a relatively small number of base colors.
For Doc Crandall's portrait I see at least the following base colors, all working together to create a smooth skin tone with some sense of perspective and depth: buff, yellow, light brown, light blue, pink, red and dark brown (or black). The colors are virtually the same as shown in Chris's test strip.
