How much red and green do you have to mix to get yellow?
It does not matter how much red (a primary colour) and green (a secondary colour) you mix together, you will always get some variation of brown or grey. Yellow is a primary colour, that means you can not mix to get it. You can't do it. Yellow is a primay color which means that you can't mix colors to get yellow. Red is also a primary color and green is the complimentary color of red. When you mix these two colors you will get a strange shade of brown...but no yellow. Sorry.