Colors vary in character according to their environment. This phenomenon is called simultaneous contrast. Achromatic borders increase the luminescence of a color. Seen against a dark background, color appears lighter than seen against a pale background. A pale background will force a color to the foreground, while a darker background will cause it to recede again. A cold color, if enclosed by a warm colored border, will appear cooler than it actually is, whereas the same color, instead set within a cold border, will appear warmer. A color code taken from a position consecutive on the color wheel to that of the foreground color will, if used as a background, decrease the prominence of the foreground color. The more complementary the background color code, in terms of its position on the color wheel, the purer and more luminous the foreground color will seem.