Ensure the 'required fields' on the donate page are more clearly 'required'

I have a hunch that some donors are reporting that "the donation page doesn't work" because it's not very clear which fields in the donation flow are required and which are optional. When you try to press the donate button with some of the required fields complete, but not all, nothing happens. There is no error warning or any indication that more information is required. I think folks are experiencing this as "the donation button doesn't work."

In this screenshot, you can see that the text "* required fields" is in green, and then the required fields are in green and non-required fields are in grey--but I find this almost invisible. Is there a way to add more distinction between what is required and what is optional?