Source : Webster's Revised Unabridged Dictionary (1913)

Erythroid \Er"y*throid\, a. [Gr. 'eryqro`s red + -oid: cf. Gr.
   ?.]
   Of a red color; reddish; as, the erythroid tunic (the
   cremaster muscle).

Source : WordNet®

erythroid
     adj : relating to erythrocytes