Excel Cell border color assignment when changes are highlighted

When multiple reviewers of a shared workbook edit the cells on a worksheet, the cells are highlighted with a color that is randomly assigned to the reviewer.  I would like to know how all reviewers could have the same color assigned that I specify.  We have to provide this worksheet monthly to a manager with highlighted changes and some of the randomly assigned colors are very difficult to see.  It is much more efficient if all reviewers make their own edits.  Once it has been submitted, we turn track changes off so that it resets to the condition where no cells are highlighted. 

Thanks for any help.