I understand the rationale for imaging at gain=75 and I'll some experiments if it ever stops raining
but I suspect most of my "conventional" imaging will be done at unity gain=139. Of course, part of the fun of the 1600 is supposed to be the "unconventional"...but any gain value below 75 is essentially throwing photons away, and in the astro game that just doesn't make sense to me...
Oh and Pete much of the information on the 1600 mono is relevant to you with the colour, as a rough rule of thumb try multiplying any exposure times quoted for luminance with the mono by 3 and you'll be in the ballpark for your colour. More importantly IMO is to check you are adequately exposing on any given night/location. It might not require exposures as long as you might think...I'd expect about 2 or 3 minutes of exposure (in a conventional fashion) would get you pretty close, depending on how dark your imaging site is.