About

An additive colorspace works by combination of colors, as in :

Addition of paint or dye is known as a subtractive model because the light reflection filters colors out

Additive primaries color are also known as Plus color

On a color wheel, they are located a 120 degree of each other.

Plus Color On The Wheel

For any colorspace, the plus color (ie additive color) are the opposites (complementray color) of the minus color (subtractive color)

This mixing are valid for all additive colorspaces (even if the most known is RGB): <MATH> \begin{array}{rrrl} & & red & + & green & = & yellow \\ & & red & + & blue & = & magenta \\ & & green & + & blue & = & cyan \\ red & + & green & + & blue & = & white \\ \end{array} </MATH>

Rgb

RGB colorspace is the most used/knwon additive system where the primary colors are:

1)

Note that

Minus Color Vs Plus Color

Rgb Addition function

let addition = ([r1,g1,b1],[r2,g2,b2]) => {
    return [r1+r2,g1+g2,b1+b2];
};