Can’t change sub-menu font

Hi. I’m trying to edit the sub-items on my site. 3 menu items have sub-items. I want to make the font bigger and change the color. I’ve tried 2 different CSS codes I’ve found in forums.

In Appearance…Theme Options…Advanced Settings and Customize…Additional CSS I tried this:

.sub-menu a {
color: blue;
font-size: 20px !important;
}

It doesn’t work even though people on the forum where I got it say it works for them.

So I downloaded the WP Add Custom CSS plugin. In Dasshboard…Add Custom CSS I tried this:

.navigation > li ul a {
font-size: 20px;
}

I didn’t specify a color because I thought I would make sure I can change the font size first. It also doesn’t work.

My url is https://thegamingden.siterubix.com/

Thanks