Hey,
You could use a conditional tag in header.php to adjust the "skin" (or colour scheme) in use on a specific category.
Change this:
$skin = $k_option['general']['skin'] != '' ? $k_option['general']['skin'] : 1;
to:
if ( is_category('category-slug')) {
$skin = 4;
} else {
$skin = $k_option['general']['skin'] != '' ? $k_option['general']['skin'] : 1;
}
You'll need to update category-slug to the category slug of the gallery category and 4 to the number of the stylesheet you want to use (located in the CSS folder).
e.g. To use /css/style3.css you'd change 4 to 3
See the codex for a full list of conditional tags: http://codex.wordpress.org/Conditional_Tags
Hope this helps!
James