Not sure whether this is what theory would predict, but if I:
Read the color values of particular graphics in an omniGraffle document on iOS (using the omniJS interface)
Email the .graffle document to macOS, and then repeat the exercise, on the same document, using the same omniJS script, on macOS …
Then a diff of the iOS and macOS outputs shows that omniJS is consistently reading the same colors to different RGB values on each platform. Is that what we should expect ?
(I have sent a sample file, omniJS script, and the differing iOS and macOS outputs to Omni Support [OG #1798194])