Help With Scss Color Customizing

[ZikmaSolutions]

Hello guys and girls, 
I am not new on prestashop but i am first time meeting with sass styles. I read about "using sass" in pretashop documentation and i know what is sass and what are type of variables. I need help with simple changing color of navigation theme. 

 

website link is: www.tech-corner.co.uk

prestashop version: 1.6.1.3.

 

What I want to change: 

http://prntscr.com/98m852

 

What I found:

.sf-menu {
	position: relative;
	padding: 0;
	width: 100%;
	
	background: $primary-darkest-color;
	@media (max-width: $screen-xs-max) { // max 767px
		display: none;
	}
}

So, I read about variables and i found this variables in _theme_variables.scss

//--------- COLORS
$primary-darkest-color:				#0A3151;
$primary-dark-color:				#005387;
$primary-color:					#007FB8;
$primary-light-color:				#6EBAD5;
$secondary-color:				#FDD922;

I changed this $primary-darkes-color to #333 but nothing happend. Can someone help me what to do?

 

Thanks