Color Theory

The primary colors of light are Red, Green, and Blue (RGB). The secondary colors are cyan, yellow, and magenta (CYM).

White light is when your brain sees all the colors together (this is why a white flashlight's light can be spread out into a rainbow). Black is when we are not receiving light energy. Grey is when there is an equal distribution of colors, but they're not at their fullest (25%, 25%, 25% or all the colors).

When looking at DIGITAL sources - you're receiving only RGB input. Your brain can then tell you any color based on what is mixed. If you look at a source in REAL LIFE, you could be seeing light with a wavelength of yellow light (most likely) or a mixture of colors (R, G, and Y). This is because your brain cannot distinguish between an even mix of R+G or just pure Y light.