The Collaborative International Dictionary of English v.0.48:

Purpureo- \Pur*pu"re*o-\
   A combining form signifying of a purple or purple-red color.
   Specif. (Chem.), used in designating certain brilliant
   purple-red compounds of cobaltic chloride and ammonia,
   similar to the roseocobaltic compounds. See Cobaltic.
   [1913 Webster]