I think not. Ασπρόμαυρο means that it has both white and black. If it's only black or only white, it's not ασπρόμαυρο but the "neither black nor white" does not apply. So you can say: το αυτοκίνητό μου δεν είναι ασπρόμαυρο! Είναι άσπρο!=my car is not black 'n white! It's (only) white!
Sorry, your comment doesn't make clear what is marked wrong ... again. You make it sound like your answer was correct and it was marked wrong and that it has happened more than once.
But what your sentence was, and why you think it should not have been marked wrong you do not state. The hints from what I see are correct.
Please make a report in such situations so that we can see if we have a problem with the hints or other areas of our incubator. If there is a problem we will correct it.
We moderators cannot see your sentence therefore before you make a comment you should have made a REPORT. Then post on the comment page.
Here's how to REPORT. Go to the bottom of the exercise page where you'll see "REPORT" Click on that:
Then choose what you want to REPORT:
-My answer should be accepted.
This is the one you should click on if your translation was not accepted.
After choosing the REPORT you want to make you should post on the comment page.