You just proved my point why my response has everything to do with the OP. You just gave him wrong information. The bulk of my second reply was in response to equippaint to answer your question but was relevant to OP. When OP said he did a C M Y K print and it didn't come out %100 true he felt, I was assuming he already made it the correct %100 CMYK values because you can't type the word CYAN in your values dialog box and poof it prints %100 CYAN. Part of your answer is right though he does need to make sure the CMYK values are correct to start.
OP needs to tell us about the nozzle check media/ink he is using and does his profile match the media/ink. If that doesn't get sorted caring about color output obtained is putting the cart before the horse.
What information was wrong? I think you should re-read his question.
He's trying to print 4 squares... one C, One Y, One M, One K. Obviously he wants a 100% Cyan, a 100% yellow.. a 100%M, and a 100%K..
Instead he got a reply telling him to design in RGB. I'm pretty sure you can't use an RGB value and get his printer to only print using the Cyan head.
Whether he has custom profiles that are bang on, or the shitiest profiles ever, it doesn't change the solution to his question. If his 4 squares are setup as 100% each channel.. All he needs to do is tell the rip to print as is, and not use a profile. I could help in onyx, flexi... but I've never used versaworks, so I'm of no help.
I do the same thing. I have a file setup to use 100% C, M, Y,K, and a mix of the lights. Why? It helps me to diagnose nozzle issues not showing up, it helps me to make sure the ink I'm using hasn't gone bad, helps to see if theres ink starvation which isn't going to show up in a nozzle check... Along with many other reasons.
The poor guys just wants to know why his 100% squares are mixing colors... And if he's at the level where he doesn't know that, I don't think getting lectured on profiles and color spaces is going to help him much.