Why is "My dresses are red." not accepted?
That would be: Benim elbiselerim kırmızı.
Aaah, anladım. Teşekkürler!
why benim and not ben?
Benim = my ...So this sentence is literally "My red dresses exist" = "I have red dresses"
But because there is also a possessive suffix on "elbiselerim", we can leave the pronoun out completely if we want. "Kırmızı elbiselerim var." More info HERE
So in that case Ben will be wrong to use?
That's right... with this sentence structure, "ben" doesn't work.