Actually, the combo of those colors could work well. If you study the color wheel, green and yellow are next to each other, or what they call analogous colors. Using analogous colors creates a soothing or calm feeling since the colors are closely related. By adding their complements (or opposites) from the color wheel, you add contrast. Reds, purples, and oranges run opposite. Mix in one (or some!!) of those, and it could be a very pleasing mix. You might have to play around with just the right shade or hue, but it could really work.