it is describing the plural "horses", and it even used the plural form of red for the "apples", so why not on the "horses"???
I wondered the same thing :(
I think it's because the plural form of 'grå' is also 'grå' :)
Im a little confused why gråe is not used because all nouns are plural...
well, grå is an adjective for both singular and plural nouns;
also there's no such thing in Danish as gråe, they've simply put that to baffle us :)
There are exceptions that should be simply remembered