How to change the background color of drop-down menu

Hi

My website is https://www.ultimech.com/wordpress

I have the menu breakdown under “industries” with 2 different colours. The code for these should be the following:

#skenav ul ul li.odd {
background-color: #75c6eb;
}
#skenav ul ul li.even {
background-color: #1d95cf;
}

I would like to have one color only so I tried to modify one of those lines above but the color does not change. What am I doing wrong?

Thanks