Ok I hate to ask a question that maybe simple but...
I read posts mainly in the classifieds and with some of the Semi Auto posts the seller will identify the color of the follower

Can you help me understand why that is significant? Previous I assumed all 40S&W were one color all 9mms were another but that doesnt seem to be true

Thanks Hank

Different versions of followers match the colors so improvements are made for improved performance.

I have not found problems with any Smith mag regardless of the color of the follower.

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Srigs

I wonder what about a follower can help the preformance of the pistol??

Sometime you dont even know what you dont know!

Different shape or contour, sometimes it does not take much to affect reliablity. I think I have black, yellow, and orange followers in 645 (4506, etc.) magazines and they all feed and function fine. But then we are talking about a 645...

As been said it usually means a change in design, sometimes a change in the mag tube itself. On the 45 mags thy added indents at the rear of the tube that required the yellow follower to clear. They changed them later and came out with black followers that would work in all the tubes. On the 5900 mags the black-to-orange allowed one more round to be loaded into them. On the 4000 the yellow-to-blue had no change other than color.