Los zapatos no son negros. ¿
O A. Cuánto cuestan
OD. Son caros
B. Qué precio tienen
C. De qué color son

The question says : The shoes are not black ? Meaning that someone ask for what color they are or what color they want the shoes in the options you have :
A: How much are they
B: They are expensive
C: Whats the price
D: what color are they

So the last one “ De que color son “ is the right one.