Are there 2 colours of Black ( Black and a Dark Greyish Black?)
Yes, I think the dark-charcoal-gray color was the earliest version from the 80s.
Are there 2 thicknesses of Hose (4mm, and one slightly less?)
Yes, the 3mm version is listed in the category "Hose, Soft 3mm D." I think there's
also a 4mm variant from about 10 years ago using a slightly stiffer material?