[CSS] Change background color of a tab

Hello,

I want to change the background of my tabs to be "none" or "transparent" and the font color of the tab text to white. I am using Design Studio 1.6.

I have tried the following css properties but it doesent fix the issue.

.sapUiTab, .sapUiTabDsbl, .sapUiTabSel { background: none !important; color: #fff !important; }
.sapUiTabSel { background: none !important; color: #fff !important; }
.sapUiTabBar ul.sapUiTabBarCnt {background-image: none; margin-top: -1px; height : 30px; background: #FFFFFF !important;border : none}
.sapUiTabStrip { background-image: none; }
.sapUiTabBar {background : transparent; }

Please take a look at my example screenshot. The white area should disappear (be grey).

I hope anybody can help me with my problem.

Thanks in advance and kind regards,

Christopher