Everything is dead in summer

I have been messing around with add on photo scenery demos to see wihch ones I liked. After uninstalling them, all the ground textures are brown whenever I set the season to summer, but the textures for the other seasons work fine. As far as I know, none of the demos replaced any of the main textures in the game. If anyone knows what might be causing this I would really appreciate the help.

Obviously can't be sure because I haven't used those particular Demos.
Past experience however has shown me that those demos install utilizing an .exe installer.
It makes sense that the developers would take great care that those installers install properly - after all they want to sell the product. Unfortunately, too many of those add-ons or demos don't give a hoot what you'll be stuck with should you decide not to keep the lovely present.

So my guess is that something went wrong with the de-installation of the demo.
How would I fix it?
Having no idea which, if any files were backed up by the .exe during installation, I'd bite the bullet and install FSX again.

Fair enough, I can do that.