so for shading red,scab red/mephiston red mix would you suggest shading with green, purple, brown or blue in the deepest shadows?
As neatly answered by MAXXxxx: any of those, depending. There's no single way to mix shadows and even if you were after one specific type of shadowing there's no generic colour guide that would be 100% guaranteed - you can't just say for example "greens neutralise reds", because in some cases a
blue would work best; and for certain reds, combined with certain greens, you'll just get brown.
I wish GW could put some kind of explanation what colours have been mixed for this blue and that pink and maybe a little describtion about how to darken and lighten it..
This bit, at least as much as most other paint suppliers GW want people to buy as much paint as they can convince you is vital and this could be seen to conflict with that*. And they may not supply all of the 'base colours' that all their mixtures are based on anyway.
This bit, is kinda covered by the above - multiple possible routes for just about all colours.
*Although you do see it in other arenas.
Now something that puzzles me is that, why there is blue? Does it have something to do with the atmosphere? I mean shadows are blue. Specially now that there is lots of snow outside, you can really see the blue shadows on a pure white snow. But would that be true if we talk about...how to put it...man made artificial light? At least I don't see much blue in the shadows inside my home.
You're right to be sceptical because when that page says "Shadows are inherently blue in hue" it's talkin' rubbish. Given the site explains colour theory based on RYB it's not much of a surprise that other parts would be equally poor; yet another brilliant example of the pitfalls to be found in various articles and other resources online about colour.
Einion