"This is white and black."
Translation:Αυτό είναι ασπρόμαυρο.
I'm not really sure why they were joined in the first place, but ασπρόμαυρος is very commonly used. There are cases where the two colors are not joined (that indicates no combination of the two), and cases where the two colors are joined, like black and white photography (ασπρόμαυρη φωτογραφία), black and white television (ασπρόμαυρη τηλεόραση), to give the meaning of monochrome. ^.^
Because here "this" is a demonstrative pronoun, standing by itself, not a demonstrative determiner standing before a noun, where in Greek you need to add an article as well.
For example, "this book" would be αυτό το βιβλίο but "this" standing on its own is just αυτό, not αυτό το.