Would I need photoshop to change this color?

Nope.. the html color code will be in your style.css file.. probably under something like:

#header {
	background:#FFFFFF;
	width: 100%;
	<strong>color: #CCCCCC</strong>;

To pick a color you can use a website like these:
https://www.w3schools.com/Html/html_colors.asp
https://www.computerhope.com/htmcolor.htm

Simply pick the color you want and replace it with the new code…