Issue with hover on the navbar for the theme mantra

Hello,

I’m using the theme Mantra (http://themeforest.net/item/mantra-portfolio-metro-wordpress-theme/4977770). I want my menu on the top bar appear in a different color when I pass my mouse on it.

These lines in style.css are not working, and I don’t understand why :

#header .jqueryslidemenu > ul > li.current_page_item > a:hover,
#header .jqueryslidemenu .current_page_parent > a:hover {
color: #1fcffd;
}

Can somebody help me ? Thanks you in advance for your time.