Watercolor in minimap

Someone successfully changed the watercolor in the minimap? Importing Water.slk doesn't work and tinting only affects the water itself.

They prolly made a custom mini map. And then imported that.

There is no simple way of doing this, and you cannot change it in the game.
To make water tinting on the minimap, you have to export the war3mapMap.blp, convert it to something other than a blp. Edit it, and put it back in.