For Nikon AF 24-50mm f/3.3-4.5D Zoom-Nikkor Lens I need instruction book. Specifically, there are dots side by side marking the apeture selected, left one yellow, right one green, what one is correct and when? Second, upper right of the apeture ring there is a pull down lever with with a white dot on it and and a corresponding orange dot.What does this do and how does it work? Thank you Rick

The green mark is the index for the aperture setting at 24mm, the yellow mark is the index at 50mm. These really only matter if you are setting the exposure manually and using an external meter. The green mark is the primary mark -- as you turn the ring you will notice that it lines up with a number at every clickstop, while the yellow one is a bit off.

The pull down lever you ask about is the aperture lock. Autofocus film cameras and all digital cameras expect the lens to be set at smallest aperture (highest number). They will give an FEE error if it is not set correctly. When you turn the aperture ring to smallest aperture you will be able to slide the white dot into position next to the orange mark, and that will lock the aperture ring so that it is not accidentally tgurned while using or changing the lens.