You can more or less easily customize the template (I say more or less because here we use Lotus Notes as the email client software), but it appears you can't modify the color of the automatic link.
Let me develop a little bit. In the mail template, there's a style for hyperlinks, however there's a kind of placeholder dUrlWithSN] that is replaced at runtime by the hyperlink... plus a span tag, containing a style with color set to #6DB33F.
As the closer style overrides the other, I always get the green hyperlink, whereas everything else is blue and yellow in my mail. Ugly.
Will I have to wait for the next update before I can get a nice link?