Theme: GeneralPress menu navigation colour

I’m trying to edit the colour of the menu navigation bar and have tried both of the below but they don’t seem to change anything

body .grid-container {
max-width: 1100px;
background-color:#F80000;
}

Have also tried…

body .grid-container {
max-width: 1100px;
color:#F80000;
}

It’s the black bar across this site https://www.ultimatesharepoint.com/

If anyone has any tutorials I could follow with using firebug and inspector tools i’d appreciate it, as it seems whenever i locate a part of the website and then locate it in a css or template file after changing it doesn’t have any effect. Could there be a master css file over-riding that needs editing?

Thanks