Source : Webster's Revised Unabridged Dictionary (1913)

Yellowish \Yel"low*ish\, a.
   Somewhat yellow; as, amber is of a yellowish color. --
   {Yel"low*ish*ness}, n.

Source : WordNet®

yellowish
     adj : similar to the color of an egg yolk [syn: {yellow}, {xanthous}]