Raws are 14 bit (or sometimes 12). But when you open them in PS you have the option of opening as 16 bit files or 8 bit. You should always work in 16 bit, especially if you are doing any serious post processing optimization, since in 8 bit you have only 256 luminosity levels, and you can start seeing banding in gradients. But I think you are talking about something else. Color fringing? Please upload a detail of the shot, or upload it full resolution so that we can see what you are talking about.

Over the years I have had issues with colorbanding in my images when I use ND filters. At times this banding can be seen on back of lcd screen if I look really close.
Other times I only notice it on the computer screen or I realize it is there after it shows up in print.
This problem has plagued me over the years and has kept me from selling many images.
I thought this should be a rare situation
Though it has been happening often.
I have had this issue
While shooting d810 with Zeiss lenses and heliopan Nd filters,
Now having the issue while shooting D850 with Zeiss lenses with breakthrough Nd filters.
I shoot raw uncompressed.
I use Nd filters for most of my work especially the 3 stop to give water a bit of movement. But use 3,6.10 and 15 stop filters.
Has anyone else run into this issue?
I notice this more often now that I have 5k iMac and also because I am printing more.
To clarify I always close eye price on optical view finder during long exposures,
I always shoot lossless raw.
This is tiypical color banding but will post examples if needed.