There is still a bunch of legacy styling code in the PHP files, but this is bit by bit being moved to the stylesheet.
The ideal arrangement would be to have the admin styling functions as is, backed up by stylesheet styling. The code would check if the admin has been changed from default and use that if so, and otherwise use the stylesheet settings for more advanced users to have more complete control.

Left & right columns are properly an admin function, enabling or disabling the code that creates them.