Thanks for your query.
Plavix is clopidogrel
a blood thinner used in patients with history of blood clots
or heart attack
The blood brown your father is spitting and red specks you saw in toilet is surely blood.
This means he is bleeding inside and willneed medical examination.
I suggest you to visit a ER or a hospital and get examined and even talk with his doctor regarding the bleeding episode.
He will have to be seen by a doctor so please consult as early as possible.