Oops!
I typed Accu-GLIDE instead of Acc-GUIDE.

I guess I've spent too many years around Electra-Glides, Wide-Glides, Duo-Glides, and Hydra-Glides!

Anyway, I digress.
The OP's question was which follower is better, not when were they instituted.
If, in fact, the blue follower does indicate switch over to the "Accu-Guide" design/improvement (whatever that may be) then it would seem that "Accu-Guide" magazines (with blue followers?) are the better ones to have.

John