The Collaborative International Dictionary of English v.0.48:

Erythroid \Er"y*throid\, a. [Gr. 'eryqro`s red + -oid: cf. Gr.
   ?.]
   Of a red color; reddish; as, the erythroid tunic (the
   cremaster muscle).
   [1913 Webster]

WordNet (r) 3.0 (2006):

erythroid
    adj 1: relating to erythrocytes