I have done a simple and cheap test. I've tested how consistent my costco printer is. It's a toronto costco on billy bishop way and most of my printing has been done there.
All 5 pictures have been have been printed within one week with an interval from 1 to two days.
None of them were adjusted by costco. All of them are shown as NNNN on the back.
Then I laid out the 5 prints and took a pic of them at f/11 to minimize vignetting. They key is to look at consistency and ignore white balance.
In real life they don't look as drastically different as they do here, but there are still very noticeable tints when you look at them side to side like that.
I'll let you draw your own conclusions:
Thanks for looking





