Mobile header troubles

I am currently designing a site utilizing the customizr theme and I am fairly new to wordpress. Not completely a new, but new enough to not know this particular issue. I have altered the code in my header to change the default from white to black. It works fine on the standard website but when I go on to my iPhone to check the responsiveness, upon scrolling it changes back to the original white. Where in the code do I alter this so it can maintain it’s black background on the mobile end? Thanks in advance.

This is the code that i have currently in my theme:

header.tc-header, .navbar-wrapper,
.sticky-enabled header.tc-header   {
background-color:   black;
}

again, i am fairly new at this so please be patient and courteous! Thanks!