You would normally set the default navigation button styles for your entire site, but you can have different looking FooBox modal navigation buttons for different galleries and pages too.
All you need to do is add some data attributes to your anchor links:
Sticky Buttons – Navigation Buttons Stuck to Sides of Browser Window
<code><a href="http://foobox.fooshowcase.com/wp-content/uploads/sites/3/2013/06/foobox-demo-pic-4.jpg" rel="foobox[1]" data-caption-title="Sticky Buttons" data-caption-desc="This FooBox has sticky buttons. They stick to the sides of the page" data-modal-class="fbx-sticky-buttons"><img alt="" src="http://foobox.fooshowcase.com/wp-content/uploads/sites/3/2013/06/foobox-demo-pic-4-150x150.jpg" width="150" height="150" /></a>
Full Height Buttons
<code><a href="http://foobox.fooshowcase.com/wp-content/uploads/sites/3/2013/06/foobox-demo-pic-4.jpg" rel="foobox[2]" data-caption-title="Full Height Buttons" data-caption-desc="This FooBox has full height buttons that stick to the sides of the page" data-modal-class="fbx-sticky-buttons fbx-full-buttons">...</a>