Door Glass - Blue Green Tint vs Clear?

[Big-Blue]

I have two sets of doors for my '71 GMC. The doors that came with the truck have a blue-green tint but the replacement doors came with clear.

Why the difference? I am assuming they are both original. The clear have the LOF imprint. I don't remember if the tinted ones do.

Is the blue-green set rare or only specific to a certain year?

Thanks for any responses.