Work is the sort of place that cares about specific colors, so HTML color hex triplets come up in conversation quite often. Neil suggested that this should be a OneBox in search results. It occurred to me that this could done via the Subscribed Link feature that we offer for search results. It turned out that subscribed links can use gadgets, which meant that an inline preview of colors was even possible. Regular expression matching also meant that I didn't have to list out every color by hand. This page has more information on the OneBox, or you can subscribe directly.

Once you have installed this, you can search for things like #fafafa or #ccc and get an immediate preview (in fact, the # can be omitted).