It's very hard to get clear contrast using pastel colors, especially shades of green next to shades of blue, which is the most common type of color blindness. Maybe use a different font? It's even worse in dark mode, where the chat background changes from grey for normal to purple for whispers. I'm not colorblind, but my older eyes didn't even notice the difference until it was pointed out to me; I was just looking for the parentheses - (GM) or (From ...) - to designate whispered text. When designing a UI, subtlety is not your friend.