As a deuteranopist, I can't tell the red zones from green. I suggest adding a few color options for different types of color blindness. A symbol on the grids might help as well.
What if you could customize the colors of the zones?
For your reference: The zone colors are actually red and a strange yellow color. The yellow color being the "warning get out," area, and red being damage zones, of course. I suppose it doesn't matter to you what they're called if you can't tell the difference though, right?
I want to be able to change the magenta color of the danger zone in game, but that's mostly because I want a crosshair that color.