Originally Posted by OziAfricana
Thanks Delofasht. I'll see how I can desaturate. Do I add white to the colours? Not sure.
Mix up a gray of the right value, scrape or wipe back your yellow and add the yellow to your gray and mix, that should achieve your desaturated yellow of the right value. I suggest a tiny touch more orange or red to the mix to avoid yellows tendency to turn green in mixes with grays or black. This should push the background color back significantly and still keep it looking like the same general color (warm yellow color).
An alternate method is to finish covering everything in the background, allow it to dry and add a glaze of ultramarine with a touch of magenta over it all to knock the yellow down and create a sense of depth. This is harder to explain because it requires a lot more operations and will likely cause the background to be darker than the more direct approach.