Does this make me half cast(mixed race)?

i know im going to get alot of abuse for this question LOL, but i dont care so, am i mixed race ?
i have an olive skin tone, my mum is white my dad is half cast (mixed race), (his mum is white and his dad is black)
and im not sure if that makes me half cast(mixed race) :S
ive always been too embarrassed to ask anyone LOL