Yellow in Classical Greek
κνηκός Note Doric κνᾱκός a pale whitish yellow
κροκός the color of saffron or crocus the flower and the pollen derived from it which Also used as a spice perfume and dye κροκό / εις / εσσα / εν
ξανθος a yellow brown an adjective used to describe blondes. Perhaps the color we would call honey blonde. The Romans translated this as flavus so the word could also be translated as light brown chestnut or auburn. I pt for honey blonde that peculiar hair color some Italians and Greeks have?
The less common ξουθος seems to be a yellowish tawny dusky yellow.
Κίτρινος is the yellow to orange of citrus fruit specific the ancient ancestors of modern lemons and oranges the κίτρον fruit.