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well when i try to open the tile set from the game files in a picture editing program. the background is blue and when i save the edited version the background of specific tiles is still blue when i place them on a map, and sorry about asking questions in this section i didnt see the general support only sentence
You gotta r-import them. Go to the materials Icon in RPGMakerXP, then go to tilesets, then import. Select the tileset you've made, and then select the blue background with left-click and a transparent colour(for shadows) with right-click.
first delete the tileset from you grpahics folder before you re-import it, else it wont let you reslect the back transparency. also make sure you saved it as a .png