You might be color blind. I noticed the same problem and I am tritanomaly color blind. You can see if you are here:

http://www.color-blindness.com/coblis-color-blindness-simula...

For me, clicking the tritanomaly button doesn't really show a difference, but my friends say it's a drastic difference.

I've lived most of my adult life not knowing. I previously thought there were just a lot of designers that picked poor color palettes. Humorously, I thought they were color blind!

I had the same problem (I'm not color blind). First game, I was light green. When dark green player started attacking me, I thought my army squares where on steroids (or something similar). It wasn't clear it was a different player killing my army.

I had the same problem when red attacked my green pieces. One of the few instances where my being colorblind is a problem :(