ive got 2 kits, 1 green pcb and 1 black pcb.

as far as i can tell here are the differences.

1. The obvious, green vs black
2. The silk screened markings on the pcb at the outer edges on the sides.
3. The tiny almost invisible numbers when looking at the back of the sticks.
a. The black sticks' number is on the right side and it is a 6
b. The green sticks' number is on the left side and its an 8

considering on the front of the green pcb you can see 1, then 2 at 2nd layer it seems to indicate how many layer pcb. so green MIGHT be 8 and black MIGHT be 6

also, the green sticks clock better for me. both sticks in the kit out perform the black ones.