Note that besides colors, there's also different surface finishes (non-finished, matte and spun metal) and prints (only the Bitcoin symbol, or also the CE/RoHS/etc. marks), and print color variations (white, grey(?), gold - at least on the silver ones). I don't think I've ever seen a truly pink Block Erupter USB, but between the various styles there's certainly a more orange-red and a more pink-red in terms of hue. Good luck collecting
Edit Just to give some examples:
Here's white markings, symbol + regulatory markings, various colors (black missing), and two surface finishes - matte and spun metal (I think was limited to the blue and red ones)
Here's the difference between non-finished and matte finish on black ones:
The non-finished ones were the early ones, no regulatory markings. The original promo image also shows the gold-ish printing on the silver unit:
Here's a good picture showing the differences in red hues between editions:
( That's from a current e-bay auction - sits at $36 right now)
