<lowest level explanation of the possibility>
You are printing with basically 4 containers of dirt, you need to mix the 4 containers to make any color that is not pure C,M,Y, or K.
The darker the color the easier, the lighter gets harder until it gets to be impossible, there simply is not enough particles (The dots of dirt being mixed) to actually achieve the color, because it doesn't have light colors to mix, it has C,M,Y and K. To make something lighter, it uses the white from the paper to do so, and to use that, it has to use less of everything else because you have to see through them, which means it has to separate the bits it lays down. This can and does cause Hue shift.
<insert from another writeup>
- Never have a gradient go from 100 all the way to Zero....90-10 is ok.
- the more CMY and K the gradient is made up of, the less you will see the "staircase" effect.
- do not have the gradient travel a long distance with a smal change.
Normally gradients look like crap on toner based output devices.
If they are running 8.5x11, they can print SEF vs LEF and have different results due to the laser lines. 11x17, you have no choice.
If they have an ES-1000, gradients print much more smoothly than if they calibrate via ColorCal as the ES-1000 samples thousands of points therefore pulling the color between all those points smoothly. ColorCal only samples a few times therefore big blocks in the gradient happen.
Sometimes, the color itself is simply impossible to achieve.(Not in your specific case here though)
You will also typically get a better quality using a PCL driver than a PS on Versalink devices, I don't know why since the opposite is true for just about every other family of printers.
I am trying to produce a pale blue image as a background to a colour document. Using various graphics editors I have taken the original dark blue image and made it progressively more pale. The image when printed remains blue down to a certain point, but if I make the image paler, the printed background becomes light green.
If I use a black original the grey background produced also eventually turns green when printed as a colour image. The only workaround I have found is to print the background in greyscale then overprint the document however I would prefer a blue background.