The ceramic material does not stain! It is her ligs that are stained.
Because the ceramic is semi-transparent, what ever color the ligs stain to is seen through to the brackets. As soon as the ligs are changed, the brackets look like new again. I agree that sometimes these brackets can look rather dim, but it is because of the ligatures.
I don't have ligs and my ceramic stays very clear!!! (see my avatar)
I have upper ceramics and lower metal and have never had a single stain on either in 7 months.

I also don't have ligs so I can happily say that I don't have even that to worry about. I can eat everything...even mustard and curry!!

To each his own and the best to everyone!