They have an excellent website!! but the addon should include a "color picker". Rated 4 out of 5 stars
I love their website.
You give the #hex code of the color and it gives you all the information you need to convert this color to other color values, such as RGB, CMYK, HSB, etc... and also color harmonies schemes, shades and Tints!!
But the disadvantage is that the addon doesn't have a picker to pick colors from a webpage.
If they add this, it will be Perfect!! ;-)