For what it's worth I might add: mine originally had a white top but the well liner is black. I don't know if it's the original one but I'm pretty sure it is....
As stated above you may have to slightly raise the car behind the front wheels and let the shock towers relax a little. I know mine won't come off without that procedure.
I’ve only ever seen black ones. Wouldn’t white reflect like crazy in the rear glass? I can imagine that the reflection of a white well liner in the sun would cause the back lite to become almost opaque....