something as simple as adding white to yellow
On second thought, this is not as simple as it sounds. The basic colors are not "symmetrical" in their perceptual properties. Yellow as such has a much higher "lightness value" than e.g. red or green, which means that "adding white" to yellow causes less of a difference than for the latter 2 colors. This is probably one reason why there is no common name for this diluted yellow. If, on the other hand, you look at a concentrated yellow dye solution (ink) it looks brown rather than yellow.