I have a room that has been decorated with plain wallpaper which has been painted a pale yellow colour but having had a radiator and shelves removed some of the wallpaper was ripped so I have replaced the ripped paper with plain white (the same as what was previously on the wall). So some wallpaper is yellow and some is the newly wallpapered white. If I put an undercoat on all the walls and then put a pale mocha colour paint on will the wallpaper that was painted pale yellow come out a different shade?