ArcGIS Pro 2.7.0
I have been knocking my head against the wall trying to figure out what was wrong with my map. I have a polygon feature class that is symbolized by category with about 17 different values (evacuation areas for a city). I could not figure out for the life of me why the colors were different in the map view vs the layout view. It is important for there to be contrast between adjacent polygons. I would adjust the symbolization and think I had gotten it resolved only to switch to the layout and see areas that did not have an acceptable level of contrast.
I could not find a satisfactory answer by searching but I did find a clue. Imagine my surprise to find out that the Color Management setting can be changed in two places and can indeed be different. You can set it at the project level under options, and you can set it at the layout level under the layout page setup. If they are not the same your map view will display differently than your layout view.
I hope this helps someone else! Map on my GIS buddies!