Menu Transition (Fade)

I am trying to get my menu items to have a delay/fade/transition whatever you want to call it, but can’t seem to get it to work. I am pretty new to all this, help is sincerely appreciated. Hoping someone may see what the problem is quickly

This is the css code I was using on my menu item

-webkit-transition: background 0.2s linear;
-moz-transition: background 0.2s linear;
-o-transition: background 0.2s linear;
transition: background 0.2s linear;

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The menu uses overlapping tabs, which are individual images.

Website is Hookahi.com