i think what he meas is he wants to change maps background color and still be able to play even tho people have other background than him...
I know exactly what he meant. But he also needs to consider what I said. If this is something for private use that isn't being uploaded to a site or something, it's no issue. But spreading around edited versions of someone else's map without proper credit is rude.
Not saying you're being rude here..but I just wanted to give a heads up, 'eh?
Edit: In response to the first reply of this topic, the type of editing you wish to do does not revolve around the scenery graphics. If you want to change the background color you have to get one of the mapmaking programs, open up the map and physically change the background color. Which is why I made that little suggestion. Unless the people you are playing with have the updated version of the map they will not see the same background color as yourself, yet you can still play with them.
It doesn't matter what you do to a map really. You can change the textures as well and still play against people on the same map. They'll just see it differently without your version on their system.