Blue in the skin.
BACKGROUND
The most prevalent theory explaining blue colors in skin is that of bluish scatter. If this accounted for blue perception, it would be measurable since a predominance of scattered blue light should emerge as a measurable reflectance. When objects are viewed with chromatic surround, there may be an increased perception of the hue complementary to their background. This effect, known as color contrast, is a well-established phenomenon and depends on the size, lightness, and intensity of the surrounding color.


OBJECTIVE
The purpose of this article is to determine the effect of background on the perception of blue color from a superficial vein.


METHODS
Fifteen subjects were asked to observe the color of skin overlying a vein on the hand. This was performed with a variety of achromatic backgrounds and with variable amounts of surrounding normal skin. Color was also measured by direct matching with standardized Munsell chips and then estimated with normal skin surround.


RESULTS
Color matching revealed the hue of the vein to be yellowish-gray, and not blue or green. Although few subjects observed green or blue with neutral backgrounds, as the vein was viewed with progressively larger areas of normal surrounding skin, there was an increasing perception of these colors.


CONCLUSIONS
The bluish color of superficial veins is more clearly explained by color contrast than by scattering. Contrast may also account for the color of certain blue nevi and may help explain some purplish colors in the skin.
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Ronald O. Perelman Department of Dermatology, New York University Medical Center and the State University of New York at Stony Brook, New York, USA.
D003118:Color Perception; D006801:Humans; D008027:Light; D012542:Scattering, Radiation; D012867:Skin / Q000098:blood supply*; D012880:Skin Pigmentation; D014680:Veins