Spectral filter means (20) in which filter elements (22) have elongated planar surface areas covered with patterns of filtering material (44, 84, 94). Filter elements are independently movable parallel to their respective surface planes to positions (32) where a given density pattern of filtering material is intersected by a beam of light and filters a given component of the light. Separate filter elements (22a, 22b, 22c) for each of the primary colors and an additional element (22d) for dimming all colors are used to control the color and intensity of a beam of light.