A good way to correct color errors in the background, or a specific spot, is to adjust color hues and saturation.

Over saturating the "main" color will expose what colors are present so you can effectively adjust the desired colors.

We find that our background contains an excess of reds, blues, and yellows.

In this case, we want a white background, so we drastically reduce the saturation and increase the lightness under main to easily reduce all backgrounds colors.

In other cases you can adjust the saturation, hue and lightness of individual colors to achieve the desired look.