Powered by Coffee is a joke logo I came up with back in 2002. As I Google around, I see I was not the only one to think of it. The 'Powered by' meme seems to have been a popular one, both in gag logos and in serious ones.
I have forgotten what the original 'powered by' logo was, but I know it was for something technology-related, and looked like something you'd find at the bottom of a web site or on the back of a computer. The Powered by Coffee people for the most part seem to have drifted away from that key concept.
The coffee stain was sort of orange-y, and everyone knows the color for coffee is green, so I added purple to round out the secondary color palette.
UPDATE:
Unrelated, but when I worked for R/Greenberg Associates back in the late 80's we bid on the opening to an NBC TV late night comedy show. I think it was Saturday Night Live, but it may have been Letterman. The client, as I recall, was Bob Pook, and his stationery was actually printed with messy, overlapping coffee mug ring stains on the paper.
I always loved that idea.
I think the first 'Powered by' was Intel Pentium chips. I could be way off though because they also have 'Intel Inside.'