Modifying a theme .php "custom_css"

I am making tweaks to my theme that I purchased (using a Child Theme) and I was able to make a change to a piece of code in a css file by using a specific selector “html .logo_sect {” instead of just “.logo_sect {“

Now I would like to change a line of code in a .php file called “css-js.php”
The line is 163 and looks like this:
http://s27.postimg.org/evs1dl1yr/Untitled_1.jpg

I tried adding this to my style sheet, but it didn’t work. Is there something different I need to do because this is a .php file or because it is a css generated from the .php file?

html .main_header {
		background:rgba(' #ffffff ',0.85);
		border-bottom:#' . $header_border . ' 1px solid;
}