According to two sources I found the answer is red. I actually thought that seemed strange and started looking into it when I saw this question here unanswered.
I found this in Michael Prestwich's book, "Knight."
"...a red cloak is worn to show humility."
A list of Catholic church associations of colors lists humility being among the ideas conveyed by red. Knighthood and Catholicism being closely linked, it is not surprising they share color symbolism.
I suppose the ideas on what color symbolizes humility has probably changed through history as I have also found mention of white and gray being the color of humility.
The color white is often associated with humility. It represents purity, simplicity, and modesty.
The color that is often associated with humility is brown. Brown is seen as a grounded and stable color, symbolizing simplicity and sincerity. It is often used to convey a sense of humility and down-to-earth nature.
a dead looking camomile
The color that represents laughter is the color yellow. The color red represents love and the color black typically represents death.
the color that represents to be organised is white
Pink. That's the color that represents their party.
Blue represents trustworthy
Blue Is the colour that represents the word believe
Yellow and black represents change.
Deep orange represents pride.
It represents red represents for bravey....It also represents Chinese people....And my last reason what does the color of china represents your moms bloody boobees
Green represents Moshi Monsters.