Here’s a convenient little Chrome extension to have handy for when you need it. It gives you the exact color specs of any pixel you’ve got displayed on your browser.
Being old school, I’ve long had a technically overkilled old school approach to doing the task: I capture the browser screen to a local graphics app like Photoshop, then use the app’s eyedropper tool to get the color specs I want from the capture. ColorZilla essentially gets rid of all that, and puts the eyedropper into Chrome, which is likely where I see the color(s) I want to get specs for in the first place: in use in a website design, graphic, or photographic image.
Speaking of photographs, ColorZilla has a cool little feature that helps with spec’ing colors from them, because heck if you’ll be able to figure out which specific pixel among its likely hundreds of thousands or more will have the exact color you want details for. ColorZilla lets you select custom areas from the image, then tells you the average color of that selection. Basically, it will let you get the specs for the color your eyes see, not necessarily what the exact color specs are at the pixel level. Neat!