Mainly black, grey and purple, although in the right amounts, most colour combo's work

I'm sure but i was told that grey and black can make white you could give it a try
but if i'm wrong than try grey and brown

Red orange yellow green blue indigo and violet

Everybody is wrong!!!!!
What is the Color Spectrum?
Think of a RAINBOW with all its magnificent color. The colors that you see in a rainbow make up the visible spectrum. The sunlight is bent by the raindrops in the air that separate the white light into all the colors we can see. Red, orange, yellow, green, blue, indigo, and violet make up the color spectrum. The visible spectrum contains light that can be seen by humans, yet there is light that we cannot see. The light that cannot be seen with the unaided eye includes far-red and ultraviolet rays, both of which can affect plant growth.

The primary colours

White light can be split by using a glass prism into seven colors- red, orange, yellow, green, blue, indigo and violet. This band of seven colors is called the spectrum of white light. This splitting of white light into its component colors is called the dispersion of white light.

The white light bends upon entering the glass prism because light travels slower in glass than in air. Furthermore, diff. Colors of light refract at different angles depending on the extent their speed slows. Violet light bends the most as it is slowed down the most. When the light rays emerge from the glass prism, they bend again, but the emergent rays are different in directions from the incident white light, as the two faces of the prism through which the white light enters and leaves are not parallel.

White light is made up of a whole range of colours ranging from red (refracted least) and blue (refracted most) at the other end.

Red,
blue,
yellow
or
red,
green,
blue

Red cyan and green-also all the colours of the rainbow

All the colours of the rainbow!!!!