How to get Hex code of any Color using GIMP in Ubuntu

First open GIMP using Unity dash or type gimp command in terminal [ctrl + alt + t]. Then open Toolbox if it is not open using 'Windows -> Toolbox' or press Ctrl + b. Now click on background and foreground color as shown in following figure.

Now in new dialog box, click on eyedropper as shown in following screenshot.

Then click on the object from where you need to get hex code of color. It will display the hex code of selected color on left textbox.

Here is the video of it for more detail.