Change top menu colour

Hello Team,

I am trying the menu colour below

I have the below code which I have added to custom.css but it doesn't seem to apply. What am I missing?

t3-topbar {
background: #468847a6;
border-bottom: 1px solid #e5e5e5;
height: 48px;
}

It looks like the color code for the background is not correct, you should check again.