Yes.
1. create a new gutter to do that
2. add that gutter to SynEdit.
in english:
1. You need to inherit TSynGutterPartBase. let's name it TSynGutterSVNChanges
in this class, your chance is override method "Paint"
What you should check? Well, you might learn & reimplement TSynGutterChanges (SynGutterChanges.pas)
2. every SynEdit has 2 place to put new gutter: the left side and the right one. (Gutter & RightGutter)
in TForm1.Create, add this line:
TSynGutterSVNChanges.Create(S.RightGutter.Parts);
I wish it help.