Race is a social construct. You are what people say you are.
My roommate in college was half-Haitian half-Portugese and identified more as European. My near 100% African-American buddy I played cards with identified himself as fully black. A half-Carib half-French (black skin tone) girl I knew identified as French. In London, a good friend who is half-Arabic half-Indian identifies equally as Arabic and Indian. My three-quarters Chinese one-quarter Japanese friend raised in Beijing identifies as pure Chinese. I think a 1/4th African 3/4ths European blood person raised in a predominantly black community would identify as black, and raised in a non-black community would identify as European.
All my data is from people who live in international coastal cities though, so maybe it's different in various provinces and less affluent middle-of-country areas.
This can and does vary from country to country--mixed-race Brazilians are considered white in Brazil, but black if they immigrate to the United States.
Of course they are.