Can I write "colour" insted of "color"?
Yes, you can. "Colour" is the British spelling and "color" is the American spelling of the same word. Duolingo accepts both versions.
why not उसकी since it is her? Thanks in advance.
My and is correct
Her colour is pink. Mai yhi to repeat karti hu.... Fir v Pta nai kyu mera ans wrong show karta h
Her colour is pink right Her colour is pink