I've tried to do a lot of altering with Blix as well and I feel the same as ladydelaluna. It's a great theme but very convoluted behind the scenes. What your looking for happens in the header.php file in the theme folder. An example is here:
else {
(is_page($page_id))?$selected = ' class="selected"':$selected='';
echo "<li".$selected."><a href=\"".get_page_link($page_id)."\">$page_title</a></li>n";
}
Altering can be very tricky but the easiest way to keep it from being highlighted is in the spring_flavour.css file. What you'll find there is this rule:
#navigation .selected,
#navigation a:hover
{background-color:#1BA6B2}
Just change the background color to #A3C159. But by doing this you will also loose the rollover (a:hover). To keep the rollover but not the highlighting, change this rule to look like this (basically just split it up):
#navigation .selected {
background-color:#A3C159;
}
#navigation a:hover {
background-color:#1BA6B2;
}
Good luck.