Most varieties can be classified as whites, reds or russets. Less common skin colors include pink, purple, and combination of white and red or pink. When tubers are exposed to diffuse light and warm temperatures for two to three weeks before planting, sprouts with color and shape characteristic of the variety are produced. Each part may vary in size and shape according to variety. The tip may be long or short and may tend to unfold its leaflets at an early or late stage.
Typical shapes are ovoid, globose or cylindrical.
Figure 7 . Color development can be localized to certain portions of the sprout. In some varieties color is not present in the base of the sprouts until after it is well defined in other parts of the sprout. Some are markedly hairy and others are essentially without hairs. The hairs may not be distributed over the whole sprout but according to variety may be concentrated on the tip, or the base, or the center.