For those with knowledge on Material Design and 508 compliance..are there any issues with using an "outlined" text field vs the filled" text field? We're thinking of using the "outlined" text fields, but want to make sure we are being 508 compliant. Any advice is appreciated, thanks!
As long as the fill or outline is clearly visible and adheres to whatever contrast standard you wish to adhere to then the only real difference between the two fields is which looks better in your design. I tend to use filled when you need to draw attention to one or two inputs in a dense design as they have slightly more visual prominence especially on colored backgrounds. They are useful for calls to action such as search fields or login fields on a colored UI component. I find outlined fields are better in larger forms where you have more space to separate form fields. The main thing is to be consistent.