Source : Webster's Revised Unabridged Dictionary (1913)

Yellowness \Yel"low*ness\, n.
   1. The quality or state of being yellow; as, the yellowness
      of an orange.

   2. Jealousy. [Obs.]

            I will possess him with yellowness.   --Shak.

Source : WordNet®

yellowness
     n : the quality or state of the chromatic color resembling the
         hue of sunflowers or ripe lemons [syn: {yellow}]