I Thought Red Blue & Green Made White?

Hi All,
I am trying an experiment with light. What I am trying to do is to produce a white light from Red, Blue and Green lights converging on one another. The problem is that the product is casting a pinkish purple color.
Any suggestions would be greatly helpful. Thanks for your time.


What is the material colour of the surface? What lind of lights are you using and how are they setup? Can you post a blend file and/or renders that display this?

I am using a cube of clear glass to shoot the light through the bottom. There are 3 spot lights. 1 of each red, blue, and green. All with the same light intensity, size, and shape. Each beam is intersecting the others by 22.5 degrees.


White is made from red blue and yellow.

Thanks for the input Lazy, but I beg to differ with your opinion. If you look at the color sliders on blender materials screen, you will seen that Red, Blue, and Green Manufacture white.
Thanks though.


Homany, I don’t know what your problem is, but Red, Green, and Blue lights form white light just fine for me.


Make sure they are all the same distance from the center. If they are angled they will soften at the far edge forming mixed colors and such. Anyway, good luck

Thanks Fliberty. Just to entertain the thought that I had a bad setting somplace, I completely closed the project and started another. Now the product is a white light. This definitely means that there is a setting off someplace, however, I have looked at everything. Well, I will look again more closely this time.


Sweet, glad to hear you somewhat figured it out. maybe just re model the cube or whatever you are doing in the scene you know that works.


Just to clarify here. Red, Green, Blue do make white. This is an additive colour space used in computer monitor screens and it models the way our eyes respond to the wavelengths of light corresponding to these colours. What you are talking about, though somewhat innacurate, is the subtractive colour scheme; if you take red paint and mix it with yellow paint, it will create orange. Red, yellow and blue (not the same shade of blue as above) will create black. Please see http://en.wikipedia.org/wiki/Primary_color for more info.

Hehe…red blue and yellow paint typically give an ugly brown actually…despite art teachers in school telling you that you could mix all colors with them :slight_smile:
As wikipedia say, the primaries in the typical substractive color space are cyan, magenta and yellow, which are basically the the complements to the RGB primary colors:
cyan absorbs red (i.e. can be described as green+blue light)
magenta absorbs green (i.e. can be described as red+blue light)
yellow absorbs blue (i.e. can be described as red+green light)

However, since in reality white light in most cases does not consist of only 3 distinctive colors, cmy black is typically brownish too.

Yeah you’re right. When you mix paint, the colours will typically not come out the way you expect or how the art teacher says; its just trial and error and also the materials used; Obviously when you buy paint or pastels, you get a separate one for white and black. It also depends the medium on which you’re applying paint. Its nice in the CG world where red, green and blue will always give you white. Light is not made of 3 colours and the RGB or CMY colourspaces can’t reproduce ALL shades/tones of colours; just a few million colours and these are enough when working in the digital medium.