Than you in advance for viewing my query.

Wanting a photo quality image of my single color geometric shape required conversion to JPEG. The reason being, the local photo shop is the only game in town when a customer wants less than ten idividual images.

Converting from Inkscape to Gimp to thumbdrive and the photoshop return's an image that in their word's "is out of gamut".

Again, I just need a single color. The photo shop adjusted my cherry red (between pink and red, for arguments sake) and the returned image came back as maroon/brown. Yuck. I don't need exact, close is good enough.

The next thought is to start at a lighter shade knowing the photoshop's machine is going to compensate darker. It would be too simple to have say, a ratio/calculation. How do artist with all their variations print an acceptable result?

The real question though, is what kind of language does a copier need, so when you create your Inkscape masterpiece you hit the print button and Shazam-Instant pretty?

Most likely pdf should be your choice for printing.
And, to avoid any "out of gamut" situations, look up how to save in cmyk colour mode.
http://www.inkscapeforum.com/viewtopic.php?f=5&t=14006&p=54764#p54764