This applet allows you to place a single, pure colored filter on a lamp. The lamp's light can be set by three scroll bars or text boxes (red, green, and blue). The color of the filter can be selected (either white, red, green, blue, cyan, magenta, yellow, or orange), and it's concentration can be varied. At a dye concentration of zero, the filter does not absorb any light and is essentially clear (represented by white). At full concentration, a red filter allows all red light to pass, and absorbs everything else. A neutral density filter blocks everything at full concentration and nothing at zero concentration.
The lamp's light starts out black. The filter starts as a neutral density filter with intensity zero. The yellow filter is a combination of red and green, magenta is red and blue, cyan is green and blue, and orange is red and half green.
If the colors of this applet appear odd to you, check the color calibration page.