Color business is difficult , when I was working at prepress 20 years ago, our manager was shouting to print house managers - they were old friends - as assholes , you need to use spectrophotometers while printing. In fact , their printers have came with automatic spectrophotometers but nobody knows how to use them ! I looked to x rite site and manual was very complex still for today when everybody uses computers and telephones. Art directors were not aware of pantone color chart use , they always want pigment color from cmyk print.
I looked to

Copper Plate Photogravure:
Demystifying the Process
David Morrish
and
Marlene MacCallum

and its about black ink printing. I dont know if there is a color gravure printing book. I dont know how you measure offset plate density before printing also ? There are meters for that but very expensive. Please shed some light Bob !
I think plate suppliers have a booklet to expose the plate. Next year , I will start studying printing press business and my goal is to be a rotogravure printer. After few weeks of holiday break , I will visit printing high school and university and collect books and notes. I love that business.
Umut