It is AMD Radeon Pro 570X. I have been working on this mac computer for 2 years now. I noticed the problem the last couple of weeks.
There is another same computer in the office working fine with the same files. It's difference is Illustrator version 25.2 (in mine it is running vs 25.2.1).
The altered colors are caused by a bug with the color management that is related to Photoshop.
As for the GPU issue: please post a bug report on http://illustrator.uservoice.com
Maybe the engineers have an idea.
I have downgraded Illustrator to 25.2, problem not fixed, then dongraded Photoshop to 22.2 and files seem OK.
Next day same problem!