I've been using the Brightside1 theme. I couldn't get the navigation menu to show a tab as selected when visiting a page, it would always go back to default green colour.

Finally figured out that the typography.css file has a syntax error in the original published theme. Change the #current to a .current (because in $LinkMode=current, current is a "class" not an "id") and the menu works as it should.

Hope this helps somebody else in the future.

Here's how to do it...

Find the typography.css file in your themes >> Brightside1 >> css directory.
Find the following code (lines 59 - 66 in the original).

.typography #header #current a {
background-position:0% -42px;
color: #FFF;
}
.typography #header #current a span {
background-position:100% -42px;
color: #FFF;
}

CHANGE the "#" to a "." in front of "current". New code should look like this...

.typography #header .current a {
background-position:0% -42px;
color: #FFF;
}
.typography #header .current a span {
background-position:100% -42px;
color: #FFF;
}

Save the .css file, do a ?flush=1 on the url and all should be good.