Kim, Without specific color recommendations I can give you two sure-fire ways to "knock down" the yellow in your work.
White paint, when added to any color really chalks it up, making less chromatic. This technique is useful as an overglaze to soften colors that appear far too bright on larger wall surfaces.
Adding the complimentary color, in your case violet; adding a little bit of violet to your yellow paint or glaze will dull it without making it appear "dirty", the way that adding black does.
Within reason, any paint color can be mixed with three good primary colors (yellow, blue, red) plus black and white. If your color is wrong just ask yourself if your color needs more yellow, blue or red. For example, if it needs both blue and red to acheive the color you want,it may be more convenient to add purple. You get the idea. Then, does it need to be lighter or darker in value; value can be adjusted with black or white paint.
Good luck,
Greg