Google's search engine has plenty of nice features, including currency and measurement conversion, a calculator and even quick word definitions. But it also has a few left-field ones, including a colour picker, much like what you'd find in Photoshop or GIMP.
Unfortunately, it's not as full featured as the tools you'll find in dedicated image editors. For one, you can't directly enter RGB / HSV / HTML codes, so if you want to replicate a specific colour, you'll have to fiddle with the selector until you find it.
It also doesn't have an eyedropper, so you can't select a colour on a web page or image to get the aforementioned encodings. Of course most browsers, via their developer tools, will let you right-click on a page element and find out its colour attributes.
You may not use Google's colour picker often, but it's nice to know it's there.