I got 2 application suggestions for Mac:
They are OS wide color pickers so they can be used to pick colors from practically anything. I like Color Snapper, because it has this zoom toggle, which zooms in really close when you hold down Ctrl. It's way nicer than increasing and decreasing the zoom level using 2 or 4 different shortcuts, which is what you gotta do in Sip. Both applications have these shortcuts that adjust the magnifying glass size up or down and zoom level up or down.
The toggle feature in Color Snapper is really handy because it's easier to move around when you're not super zoomed in and then zoom in when you are over the area where you want to pick a color by using just a single modifier key. If you want to do the same thing using these shortcuts, it's a big hassle. That's always been the big selling point for me. That said, Sip does have some more features.
I do also like that with Color Snapper you pick the color and then it suggests the different output formats, whereas with Sip, you gotta choose the format first and then pick the color. It's not a big deal though... If you pick a color in the wrong format, you can change the format and copy the color to your clipboard again from the color history.
Sip does give you CMYK, while Color Snapper doesn't. They both have trials.