Symbolizing using RGB values from Excel in ArcGIS Desktop? and Symbolizing vector features using RGB values stored in three fields using ArcPy? are questions that distil to whether it is possible to use RGB values in fields of an attribute table to apply colours direct to a feature layer in ArcMap/ArcPy. It seems not to be possible so I advised voting for an existing ArcGIS Idea (for ArcGIS Desktop).
My searches of the GUI and web for the equivalent functionality in ArcGIS Pro have also proved fruitless but I am hoping that I am wrong.
Is it possible to use RGB values stored in a field of a feature class to apply the colour component to symbols used to display them in ArcGIS Pro?