Look up: RG color space

1. RG color space
   The `RG` or `red-green color space` is a color space that uses only two colors, red and green. It is an additive format, similar to the RGB color model but without a blue channel. Thus, blue is said to be out of gamut. This format is not in use today, and was only used on two-color Technicolor and o...
   Found on http://en.wikipedia.org/wiki/RG_color_sp
   
   
2. RGB color space
   An `RGB color space` is any additive color space based on the RGB color model. A particular RGB color space is defined by the three chromaticities of the red, green, and blue additive primaries, and can produce any chromaticity that is the triangle defined by those primary colors. The complete speci...
   Found on http://en.wikipedia.org/wiki/RGB_color_s
   
   
3. RGBA color space
   `RGBA` stands for `R`ed `G`reen `B`lue `A`lpha. While it is sometimes described as a color space, it is actually simply a use of the RGB color model, with extra information. The color is RGB, and may belong to any RGB color space, but an integral alpha value as invented by Catmull and Smith between ...
   Found on http://en.wikipedia.org/wiki/RGBA_color_