RGB colors?

What are the RGB numbers for Grey, White, Green, Blue, and Purple?

You mean the player color codes, or just general colors? I assume you mean in general, as white is not a player color. Well, let's see, green and blue are basic colors, white is a mixture of all colors, grey is same as white only darker, and purple would be a mix between blue and red.

The color code format in warcraft is |cTTRRGGBBput your text here|r, where T is transparency, and R, G and B are respective basic colors red, green and blue. The format is hexadecimal, so it goes from 00 to FF (which equals 255 in decimal format). 00 means completely transparent or no color, while FF means not-transparent or full color.

For exact player color codes, look here

I'm talking about Unit Tinting RGB

That's similar. The values go from 0 to 255 in the object editor and from 0 to 100 with the unit vertex coloring action in the trigger editor. 0 means that color is completely removed from the unit, 255 (100) means that color is fully present. This means you can only make the units darker by removing a certain color from them, you can't make them brighter. To make a unit blue, just reduce the values on red and green.