I don't role play and this is getting silly fast. This is what you need to know:
Eredar is the race. After Sargeras did his shtick with Archimonde and Kil'jaeden, the eredar split into two. You have the man'ari eredar which are now demons (or corrupted eredar) and the draenei which is a name in their language given to the non-corrupted eredar (or one could say "original, pure" eredar) which is also the playable race.
Lorewise, you could technically spin it saying the draenei are a race themselves now since the man'ari eredar are now demons (demons being a race in its own right) but if you plan on roleplaying your DRAENEI character as an MAN'ARI EREDAR... your best bet is to find a skin tone that is close to red, dark purple, or even pale greenish-blue.
EDIT: I meant to add that the draenei are the original eredar; they just do not call themselves that anymore.