TOPIC:

I'm building an XOT and using the Modern Sleek Gray template.
Within this template, the titles of the tabs are blue. How can you change this color?
What css code do i need to write to change this?

What page type are you using and referring to? Do you mean the background of a selected tab in a tab navigator is blue?
If so try:
.ui-state-active a, .ui-state-active a:link, .ui-state-active a:visited{
background:#F00000;
}
But learn how to use the browser tools to find the selector you need on a given page element e.g. right click and select inspect then look at the styles and explore changing values until you find what you need.
HTH
Ron