Menu Text Colour

I would like to change the text colour in my menu, site-title and site description. I would like all text (except highlighted menu and current menu item) to be black when scrolled right up and white when scrolled down. Also when scrolled down I would like to change the colour of the current and selected manu item. Hope that makes sense.

Here is my current custom CSS

.home #content { display: none; }
.site-header.float-header {
    background-color: rgba(34,135,244, 0.9);
	l
}
@media screen and (max-width: 1024px) {
	.site-header
	{
		background-color: rgba(34,135,244, 1);
	}
}
.site-title{
	text-align: center;
	border-bottom: 5px Solid;
	border-color: rgb(255,255,255);
	font-size: 30px;
	
}
.site-description{
	font-size: 24px;
	text-align: center;
	vertical-align: middle;
}
.promotion-message{
	background-color: rgba(255,255,255, 1);
}