As you have figured out, the game only uses files with certain names. So, to "delete" the mods you don't want to use, simply rename them as you said above and the game will no longer see them to use them. Or, you can simply delete them altogether. To return to using the original images, go to the folder in which you saved your backup copies and copy the file you need. Just paste it into the game's image folder and you should be good to go.

I would think that the blue is due to missing images. Check the backup folder you made and look at the list of maps. Make sure you have a map in your actual game folder matching each name listed. Locate the ones missing and just copy and paste them into the game's folder.

You may find your mods don't match up. If that's the case, I would just copy the entire set of maps from the backup folder and start fresh with those.