If you are using a phthalo green (blue green) you can add a cadmium red plus white. For details on ratios to get the gray, use the related link below
An even amount of each colour. But to get a dark green colour add more blue, and to get a lighter green add more yellow.
yellow
To turn green black, add black.
white
Yes they add colour to it to it brown
Red is a base colour. You cannot mix it from other colours.
You would get yellow if you add green to red because these two colors combine to create the color yellow in the subtractive color model.
For the green they add yellow and blue color aditives. For the brown they add red, blue, and yellow color aditives. Simple as that.
Red. You can't make a pimary color out of a secondary color.
green and this is definite because it came up in my GCSE's and i got it right
The mixture of any secondary colour and the primary colour that is not part of it will result in a brown. For example: Add yellow to purple. Add red to green. Add blue to orange. You could also just add blue and red which makes purple but if its dark enough it might be able to produce a brown-ish colour. If its to purple then just add black to it.
Sage green is basically a greyed green. Start with a medium green add white to lighten the shade then add a touch of black to grey the colour down.