How come my printer will print in color fine but when i want it to print in black it prints grayscale?

How come my printer will print in color fine but when i want it to print in black it prints grayscale?How come my printer will print in color fine but when i want it to print in black it prints grayscale?
Did you check your printer settings? Are you sure you have black ink? Sometimes if you run out of black ink it uses the colors and the output looks grayscale.