1. Change the colorby_default bit
In the database, look at
select * from colorby

if the default is not what you want, then change it. For instance, if you want the default to be Space Function, then use this SQL:
update colorby set colorby_default = 0 where colorby_default = 1
update colorby set colorby_default = 1 where colorBy_name = 'Space Function'

2. Restart Statics/Restart Domain

3. Refresh the MAC drawing files
In the database, look at
Select policy_DWGFolderPath from policy

For the path that comes back, delete all *.SER files from the directory. From the image_cache subdirectory, delete all *.GIF files.
Open up a drawing from the MAC – the new colorby appears.