Well, as I said, the colour is still yellow, as you can see from the RGB values taken from the pictures.
If still you want to get a lighter colour on the wall, you may try to change the brightness configuration of the wall, or cheat a bit and put the wall directly on a yellow slightly lighter than the one on the floor, so the final result comes closer to what you're expecting to see.
----------------------------------------
If a long walk every day were healthy, mailmen would be immortal.
