I think, she's wearing a cloth which refelects sunlight. Do you that? It has a smooth and shimmering surface. If there's litte light it looks orange, when there's a lot of light yellow and if there's a lot of sunlight, it looks gold and pices of yellow.
I think it doesn't depens on canary, or not. In our countries version Kuja compairs her with a pigeon...
In my opinion it depends on "Garnet". A Garnet can have many different colours. It's usualy red, but it can be orange, too.