Our perception of color varies a lot based on context—size of the swatch, background color, surrounding colors, etc. It is unsurprising that even on sites with a seemingly-consistent color palette, you'd see a lot of variation. Colors that are "the same" will also vary based on how they're being used, e.g. I might use "the same" blue for a highlight as I do for a shadow, but if you look at the RGB values, they're totally different. The reason is that your brain is seeing a shadow, and separating the brightness component (reduced, since it's a shadow), from the color component. Man, isn't your brain incredible.<p>It would be interesting to take this script and make it so that it does some kind of clustering, or looks at different components of the color—for example, you could just count the hues. One might expect to see a lot variation in lightness, but relatively little in hue, for example. On the other hand, maybe it's not that scientific, and designers just grab a color picker and fiddle until it looks right.