I don’t know your level of comfort with trying something like this, but here it is anyway….
The color is kept in the project file (in Premiere Pro 2.0) or the PRTL file in earlier releases. A simple text program designed to find and replace could change all of the colors in one pass.
Just use a copy of the project to do this. If you can’t find the location of the color, change one using the copy of the project and then compare the two text files with a text editor (MS Word will do the job).
I have a program I like for that, but I am away from my editing PC at the moment and can’t remember the name of the app.
Steven
https://www.stevengotz.com