I was reading the following article by Todd Klein (DC Comics 1977-1987) and was inspired to make this palette.
Coloring Comics, Old School
I have used the 25%,50%,75% and 100% values of Cyan, Yellow and Magenta that the color separation house would have prepared as denoted in the article.
I have named each value in this palette after their cymk ink values eg/ the 25% yellow ink will be named 'C0 Y25 M0 K0' and the 50% magenta ink would be named 'C0 Y0 M50 K0'
K or the Key Colour is Black and is not contained in this palette. You will notice that 100% of cyan, 100% yellow and 100% magenta mixes to 'mud'. So do your inkwork in black R0 G0 B0 first then load up this palette to colour.
Because all colours were originally derived from CYMK values they are obviously within gamut and can be reproduced in printers inks.
As noted in the article the 75% values did not appear until the early 80's so if you're going for an authentic retro look avoid any colours that have the number 75 in their title. If you are trying to make things look old you may need to fade and beat up the colours a little. If you want to start on a paper that looks old R=250 G=230 B=190 is a good starting point for colour (tweak as you like)