Someone emailed me last night with a question about the phrase "the deep purple" -- not the rock band or the song by Peter De Rose with lyrics by Mitchell Parish, but the phrase as used, for example, in this line from a play written in the early 1900s:
I want to say mister, I've met a lot of game men in my time, but by God you're bred in the deep purple.
I would speculate that the phrase "the deep purple" is a reference to the ancient tradition of purple as a royal color. In ancient times, it was quite expensive to produce purple clothing -- the dye was mainly derived from the shells of the murex (a kind of mollusk), for example as found off the coast of Tyre in southern Lebanon (thus Tyrian purple). Thus purple clothing tended to be reserved to the royalty or nobility. This usage survives in phrases like "purple prose" to describe an ornate writing style and "purple passage" to describe writings that have gained kudos because of their noble qualities (an example might be Hamlet's soliloquy). So to be "bred in the deep purple" might mean something like being born with a silver spoon in one's mouth or, more positively, to have noble blood running in one's veins. This seems consistent with the quote provided by my interlocutor. But, again, that is speculation on my part.