Nice to see an alternative app for this. I made one a while back - https://apps.hoyd.net/hexcolors/ which does the same using flask, python and bash. Been using it quite a bit for extracting colours from images. Also set up a Twitter not to find colours in satellite imagery: https://twitter.com/FiveEarthColors
I'm the developer of this little website. Really excited to be on HackerNews. It is really a pleasure to see so many people like it, so I decide to opensource it. You can check the source code of it here: https://github.com/Hopsken/colorkitty.
And, thanks for all the kind advice. You guys are really awesome.