The color-matching prism, the so-called color combination means that the light can be divided, and there are four light-transmissive surfaces, which can ingest white light on any one of the light-transmissive surfaces, and can emit three kinds of red, green and blue from the other three transparent surfaces.
The base color light is the three-base light. This is spectroscopic.
There is also the light, which is to ingest red, green and blue light from any of the three transparent surfaces, and will emit white light from the remaining one.
This is the combined light. It is said that it is possible to divide red, green and blue into white, and it is possible to divide white into red, green and blue.
This is an important accessory on the projector. The projector can project color on the screen.
You should know that the color on the screen is composed of three primary colors. The color prism is an important prism for forming three primary colors.  
Principle of color prism:
The dichroic beam splitter is a color separation element in an MD projector.
A light-splitting film is plated on the substrate glass, and the white light source is irradiated on the dichroic beam splitter, and light in a part of the band is reflected, and light in a part of the band is transmitted.
Since the wavelength bands are different, different color lights are present in two directions.
This dichroic splitting principle is used in projector optical engines.
Two dichroic beamsplitters are used to plate two different spectroscopic films to decompose white light into R, G, and B primary colors.
It is also possible to use a dichroic beam splitting principle to form a color combining prism, and combine the three primary colors to form a color image.
Material: Quartz