Sampling a color in The Gimp is easy. You just click on the eye-dropper and then click on the section of the image you'd like to sample.
The exact color of the sample is then given as a RGB number expressed in both hexadecimal and decimal. Once you've read that number, you can close the dialog in which it appears.
I find clicking on the eye-dropper icon in the toolbox inconvenient. Instead, I prefer to use the keyboard shortcut. For me, this is the simplest way to get to the color sampler tool.
Both the tool icon and its equivalent shortcut are nice mnemonics.
It's easy to remember the visual way to get to the color sampler tool if you just think of a bucket of paint. Visualize the eye-dropper taking a small sample of paint from that very same paint bucket.
If you want to remember the keyboard shortcut for the color sampler, visualize the bottom of the eye-dropper. It is round like a lower-case letter ``o''. Pressing the lowercase ``o'' makes the eye-dropper the active tool in the toolbox.
Note that the eye-dropper does not work at all unless the image you are sampling is active. An easy way to make the image active is to click on its title bar once.
©Edward Abbott 2004