Opacity Option Greyed Out (unavailable) in Image-Substitute-Color Dialog Box
When I attempt to change colors using the Image-Substitute-Colors dialog box, I almost always get the "Set opacity of the new colors" part of the box "greyed out" and unavailable for use. In a few rare instances it has not been greyed out, and I was able to use it, but I cannot figure out what makes it work in a way that is consistently usable. When making these kind of changes, I always save the file as a GIF so the opacity / transparency information is supposed to be saved with the image. This same behavior shows on my corporate environment machine running 7.29.94 and also my personal home machine running an up to date self-purchased 8.13.00.
Thank you in advance for your help