To change the colors you will need to edit the
more_share_options template.
There are several places you may try to make the edit, since you have a custom style I can't tell you for sure which would work.
First I would try looking at the line:
Code:
<table class="tborder" cellpadding="0" cellspacing="1" border="0" width="100%" align="center" height="22">
And adding a background color to it:
Code:
<table class="tborder" cellpadding="0" cellspacing="1" border="0" width="100%" align="center" height="22" style="background:red;">
For example.
You will need to know some basic HTML to get the exact colors of course.