I think the oath allows room for generally true statements without needing qualifiers.
If asked "What color is that cat?" an Aes Sedai could simply answer "black" without having to say "with yellow eyes and white a small white spot on the chest".
"What colour is the sky?"
"Blue."
Likewise...
So glad you decided to do this Laurien, it's delightful!
I think it would have been really funny to do the colour shifting by randomly changing out the cloak for one of a different colour each time they did a take. As if they were deliberately ignoring continuity. So we'd never see it change...