I don't know if you've solved this yet, but here is what I have figured out.
I define a style to be applied to those tokens in my SKIN.XML file
<!-- Class for the login control -->
<Token>[LOGIN]</Token>
<Settings>
<Setting>
<Name>CssClass</Name>
<Value>UserStyle</Value>
</Setting>
</Settings>
</Object>
<!-- Class for the USER control -->
<Object>
<Token>[USER]</Token>
<Settings>
<Setting>
<Name>CssClass</Name>
<Value>UserStyle</Value>
</Setting>
</Settings>
</Object>
(I do skins in HTML, if you use Vis Studio or Express, you enter the style directly as a property I think)
Then in your style sheet:
/* style for User and Login tokens */
.userstyle {
color:#000000;
font-size: 80%;
font-weight: normal;}
a.userstyle:link, a.luserstyle:visited, a.userstyle:active {
color: #0D3257;
font-style:normal;
font-weight: normal;
text-decoration: none;}
a.userstyle:hover {color:#0D3257; text-decoration:underline;}