Yellow

Yellow is has the highest symbolic value in Buddhism through its link with the saffron robes of monks.

This color, previously worn by criminals, was chosen by Gautam Buddha as a symbol of his humility and separation from materialist society. It thus signifies renunciation, desirelessness, and humility.

Yellow is the color of earth, and thus a symbol of rootedness and the equanimity of the earth.

Source

http://www.religionfacts.com/buddhism/yellow