The small weight is where you want to pay attention. The ones above, the small weight is very thin and therefore light. The small weight controls WOT upshifts, the lighter it is, the higher rpm it will shift. If you see a bunch of standard govs and you compare it to the ones pictured above, you will instantly recognize the thin weight. I do believe there are actually 3 sizes, but the heavier two are visually different and thicker than the ones above.
You CAN whittle down a standard gov but it takes a lot of work and then you will have to trial and error the shift points and drop the pan each time.
Gear color is not important. only difference between colors is the speedo drive gear part, and you can make almost any of them work for you with the proper driven gear and if not they are easliy swapped out. BUT the GN had an orange gear from the factory with 11 teeth on the speedo part and the green is MCSS and has 10 teeth.