Red, green and blue. And not just green, but really GREEN! Where are the colors today ? It seems that modern gaming only uses brown and gray. Which seems logical considering their atmosphere, but looking back; all the violent of the 90s seem to have colors!
Look at Mortal Kombat for example, one of the goriest and bloodiest game series of 90s. it left parents in disgust! Yet it had a vibrant color palette, from light green to light purple to orange and blue.
I wish games nowadays had a bit more color to them :)