Since το χρώμα (the color) is a neuter noun, we use the neuter gender to refer to itself, although we use the masculine or feminine gender to refer to it as a characteristic of a masculine or feminine noun:
το μαύρο χρώμα
ο μαύρος σκύλος
η μαύρη γάτα
τα μαύρα μάτια
Foreign words like μπλέ do not change to show case or number: