What about 'I do not like white couches'?
I think "I do not like sofas that are white" is better.
I don't think Duolingo is doing a good job of translating "yang". It should be used like "that is" or "which is" when used like that.
They are dropping the ball on the plural/singular here as well, with my answer getting alert that 'sofa' being typo of 'sofas', but there isn't context to say whether it's generic sofas or specific sofa that one does not like.