Why does Illustrator distort colors in a PDF created on the server?

Question

PDF

A printable PDF is created on the server using Prawn ( https://github.com/prawnpdf/prawn ).
In the preview it looks like this (correct):

In illustrator it looks like this (not correct):

Answer 1

Problem solved - no color profile

Answer 2

And who knows him?
I can suggest a way to investigate the problem: create a test PDF, as easy as possible, in Prawn. A pair of rectangles and a letter, for example. Open it in Illustrator, bring it to life (if it doesn't look right), save (using the settings of the same PDF version), compare the original and the resulting one, find the difference.
Illustrator and Acrobat contain "reference" code for working with PDF, so if something is created outside of them, and it does not look like it should, this means an error in that software (or in its settings, which is more likely) where PDF created, not in Illustrator.
Here, I dare to assume, some kind of curved color profile is applied, or it is applied correctly, but incorrectly indicated.