Green is never quite green

One of the things that I learned when sewing was to be very careful with color.  Because I spent a lot of time making military types of equipment, color and color matching was very important.  Take green for example; even if we limit ourselves to four greens you can see they vary considerably. 

This means you can't just mix them, you need to pay attention to which green you are using.  Different military and police branches use different greens. The Army tends to use Olive Drab, the border patrol uses Ranger green etc.  Camp green is a bullshit color used by no one except some cheaply made stuff.

It's even worse with camo patterns as there are so many!  Using the wrong fabric color on a piece can can cause problems.