Color banding appearing on screen of gray image?

[Brian K]

Here's something I just can't understand. I've started scanning B&W negs of nighttime scenes. The scans are 16 bit rgb but the end result is a gray scale image, desaturated and lacking any real color. However in the deep gradation of the night sky there appears to be a subtle green to magenta banding. It does not appear on any prints, even color prints, and does not register as having any color banding when checked with the eye dropper.

To make matters even more confusing, even when I convert the image from 16 bit RGB to 16 bit gray, or lab, or CMYK, the banding still appears on the screen. This banding appears on both my Eizo coloredge and iMac monitors. I'm assuming it's some sort of color space issue but again it appears as an sRGB, Adobe 1998 RGB and Grayscale gamma 2.2 color space.