By linda from McDowell, KY
Paint your wall yellow!
My suggestion is to do the same thing as people used to do 50 years ago, 100 years ago and even more years ago than that; and that is to wash the walls (a simple vinegar and water or soap and water solution with a rag) every month or so. The cleaning was much worse way back then when it was wood or coal for heating than gas is so count yourself lucky. ;-)
I used nail polish remover. It worked better than vinegar for me.
You may want to test an inconspicuous area if using nail polish remover. Then hold a light near the wall and test area. Remover will probably clean it. However, it may discolor the paint.