Highlight One Main Nav Item

Hello. I saw you answered this in the High End Theme, but not for Aegaeus theme.

In my main nav, I want to put “LOG IN” nav item on a green background always. This will essentially highlight the log in link.

VegasAuditions – Home

I’ve tried two ways and still can’t seem to get it to work:
1. I added this to the child theme style.css

#menu-item-3345 {
background: #43bc54;

2. I added this code to the CUSTOMIZE theme (add your own css code) section:

li#menu-item-3345 {
background: #43bc54;

Neither seems to work. Any suggestions??

Thanks.