Unlike all other meteor showers, which originate from comets, Geminids originate from asteroid 3200 Phaethon. Seeing a large number of meteors last night, I noticed they seemed to be much more green than other meteors, but is there anything else I should expect to see different to other meteor showers? Brightness, size, length of trail etc?
Well done on your observations, I've been completely clouded out.
You are quite right, the Geminids are noted for a variety of colours, and a good number of fireballs, though most observers note a predominiance of yellow meteors This is partly due to their composition and density (coming from a peculiar "rock comet") and partly to their velocity (35km/s) which is fairly fast.
There is a good chance of seeing some good trails with this shower. Brighter meteors and most fireballs will leave a trail, and the Geminids have more of these than most other showers.