PDF documents created with Plots don’t have a color profile assigned to them, so it’s possible that when your publisher opens the file, they assign (automatically?) the wrong color profile to it (Like Josef, I wonder whether they’re overdoing it with a conversion to CMYK?).
If you can process your file and save it as PDF/X, with an RGB color profile, this might behave a bit better at preserving important aspects of the original. PDF/X is designed to be better for preserving the original document’s intent as it passes through the printing pipeline…
But with printing generally, you can only do your best before the recipient takes control…