If you are a client and are hiring people and paying them money, I don't think anybody cares.
If you submit a nice-looking black-and-white photo, nobody is going to mind.
If you are a freelancer and you are setting up a new profile page, and you want to avoid any possible problems that could delay or block your profile from getting approved, then don't mess around with color filters.
Look at the information page Upwork provides describing what kind of profile photos it wants to see. Use that as your guideline. If you want to get approved and start earning money here, then it's not the time to do things that might tempt Upwork representatives to reject your profile.