"Ποιο φόρεμα είναι κόκκινο;"
Μετάφραση:What dress is red?
Just let's hear another opinion from one of the moderators of the lesson. It is holiday period in Greece so it could take a little bit long (I don't have any rights to edit the messages, as I am not in the group of the creators of the lesson). Give us some time :)
You are not wasting anybody's time, you are helping us to improve the course. You have a good point, and even though it is not grammatically incorrect, it is not commonly used, so we are removing this one. This exercise was in the group of the word "what" we are going to replace it with something along the lines "what color is the dress"!