Changing the style for the drop down submenu

I want to make the submenu color black and left aligned. The following style should do it:

div#page .upfront-output-region-container .upfront-output-module .default div.upfront-navigation[data-style="horizontal"] ul.sub-menu > li.menu-item > a{
color: #000000 !important;
text-align: left !important;
}

But adding this to the global CSS or regional CSS, doesn't matter, it doesn't take any effect.