I have probably seven magazines that will work with the 4506 and 4566TSW. Two or the originals have orange followers and one has a yellow one.
I bought half a dozen new mag springs from S&W not long back and decided to get some followers as well. All these were black but look no different to me than the others.
When is there a need to replace the followers other than maybe an obvious sign such as a crack or torn edge? I've always been curious about the slightly raised indent on top of the follower and it's purpose. The old ones, naturally, are worn down somewhat and other then perhaps giving the cartridge rim a little "kick" upward right before cambering, I see little use for it.