加色法是描述那些由不同颜色的光混合形成新颜色的情形。这是对比光线从各部分的可见光谱创建颜色的减色；电脑显示器和电视是加色法最常见的形式，而在油漆、颜料和彩色滤光片会用减色。用加色产生颜色时，通常使用红色，绿色和蓝色光来产生其他颜色。把其中一个加色原色与另一个混合会出现加色间色​​:青色、洋红色或黄色。彩色像素在显示器屏幕上不会重叠，但足够的距离时，光线从像素扩散到视网膜上的重叠。加光的另一个常见用途是用于舞台灯光，如戏剧，音乐会，马戏表演，夜总会等。

Additive color is color created by mixing a number of different light colors, with shades of Red, green, and blue being the most commonly primary colors used in additive color system.

Additive color is in contrast to subtractive color, in which colors are created by subtracting (absorbing) parts of the spectrum of light present in ordinary white light, by means of colored pigments or dyes, such as those in paints, inks, and the three dye layers in typical color photographs on film.