Personally, I find Firefox to be the best browser for debugging purposes. It is widely known as the most lightweight browser with numerous addons available and a strong commitment to web standard W3C.
Essential addons like Firebug, Webdeveloper Tools, FirePHP, and Colorzilla are highly recommended. Instead of searching on Google (for security reasons - remember the keyword is the mozilla domain), I suggest using Firefox's built-in addon search feature.
When it comes to color, utilizing Colorzilla Eyedrop allows you to easily sample any color on a webpage. Then, use Webdeveloper to pinpoint (with just a click) the specific part of the page where this CSS rule is applied. There are plenty of resources available so there's no need for me to repeat what has already been well-documented.
These tools will provide you with a comprehensive toolkit for solving various issues. Installing them should take around 10 minutes if you don't have them already, and the user interface is excellent, making it unlikely that you'll need to consult any additional instructions.