I'm pretty disappointed in Vistaprint's color correctness. They maintain that the color in their editor is "black," but it's a clearly a charcoal when printed, and they blame the images I uploaded (which were CMYK, definitely black) for not matching. Your "black" doesn't meet printing industry standards, +Vistaprint
. Don't blame me when your example shows it looking perfect, but your printer prints something that doesn't match. If you show a result to someone and ask if it looks right, and then ship something that looks different, there's a problem with your printing, not with your customer.
After analyzing the issue, I've figured out why it happened, and it's this: Vistaprint uses different blacks. "True black," which appears darker, is CMYK(75,68,67,90). VistaPrint uses a "false black" when printing which appears lighter CMYK(0,0,0,100). Though truly absent of color, it appears a charcoal color next to true blacks, which with more blue appear on printing to be darker. Regardless of this, their preview online showed the colors next to each other to be identical, which was clearly not the case.
Why does their online preview differ? Their online preview, being a web tool, uses RGB(0,0,0). RGB(0,0,0) is true black in the printing definition, which is CMYK(75,68,67,90). But when they print it they use CMYK(0,0,0,100) which is RGB(35,31,32) - so their printing colors do not match their design colors. This is a serious issue. I will not order from them unless they can resolve this in the future.
Fix your stuff, Vistaprint. Your design should match your result. That is why your customer got a refund today. They were not mistaken, your prints do not match your designs. Adjust your editor or adjust your printing.