Hey Eileenp,
Thanks for your question and welcome to the community!
Your 48" Hampton Bay Roanoke ceiling fan does have a darker than usual glass, you are correct.
Before contacting Hampton Bay directly, I'd first recommend to use a brighter bulb in the fan. We carry energy-saving CFL and LED lights that come in higher color temperatures like daylight that are much brighter than normal softer whites. Try one of these out first to see if this will solve your problem. If you have already, then disregard.
As for contacting Hampton Bay, they can be reached at the number below. I know we carry the same fan in white, so you should be able to get a replacement globe that is not so amber in appearance.
Let me know if you have any additional questions, and keep us updated on your progress.
Joseph