Change Tracking Options
Microsoft Word 2007 lets you select how you
would like to track and display the changes. You can even select
which colors you would like.
Try it: Change the Tracking Options
Go to Review -> Tracking.
Select Change Tracking Options.

What Do You See? At the top of the list are the
Markup options. By default, the color is assigned by Author.
Anything that is deleted is formatted with a strikethrough
like this. Again, each
author gets their own color.