 So you know how to paint, but that's too much work. Not a problem. If you have a landscape in selection mode, if you shift select the grids that you want to color, then in the Outliner, you can actually just drag a material straight into the material slot over here. Once you do, if you double click the material, you will be able to adjust the tiling to better fit your landscape. And if you want to change the color hue of the environment, you can actually do that by going back into the material and changing the Albedo amounts over here. Hope that helps and as always, hope you have a fantastic day and I'll see you around.