EditMarks can have up to 248 revisions, each revision can have its own colour.
To create a revision click the new button on the EditMarks palette. The popup menus will now show 1 - 1.
If EditMarks is being turned on for the first time a new revision will be created automatically.
Any EditMarks created before revision 1 are automatically included in the first revision.
If a document has 10 revisions and the popup menus are showing 3 - 5. The EditMarks below 3 and above 5 will not be drawn, they are still in the document.
On Windows when you change the revision popups, EditMarks will change the view to caret view.
More about revisions.