That's the risk you take with a bounty. Once the bounty is set you lose the points.
No one is under any obligation to answer your question and if no one knows the answer then they're not going to answer bounty or not.
I can only suggest that you add any extra information you've managed to find from your continued investigations - you are still actively ...
What should I do if no one answers my question?
First, make sure you’ve asked a good question. To get better
answers, you may need to put additional effort into your question.
Edit your question to provide status and progress updates. Document
your own continued efforts to answer your question. This ...
Nice to see your question answered. I would say (in this particular case...):
Cut Asymptotically some slack and give him his 50 rep. back (upvote question on WebApp)!!
Here is the Q&A : Google Calendar colorize weekends in Firefox