What is actually youre issue ?
The water is like that due to a scenario design choice, map setting and terrain blending.
it’s supposed to represent a specific water region with specific water look.
It’s called “combined terrain”, a land tile combined with a water tile, with eventually “no-wave” parameter.
It’s intentionnal map design style, to make it look like a swamp I’d say. There is also a parameter that drives the map water appearance style.
Do you have the issue anywhere else than on this map ?
Eventually, if you’re Color-Blind, there is a setting for that, it may explain why you think there is an issue, while my eyes see none.