You may think that it shouldn't be that difficult to promise exact colors- but it is!
When it comes to online printing services, the translation from what you see on your screen to what you see on the printed piece that arrives at your door is more complicated than you might think.
Professional printers also use a 4 colors to create all of their images (Cyan, Yellow, Magenta, and Black). Your computer monitor uses RGB, and colors and be bright indeed on your monitor. Have you every tried printing out your own design, a design with delightfully bright colors, only to find yourself with a printed color that was much duller, washed out, than you wanted? This is because the color you wanted actually isn't actually printable without highly specialized means.
When it comes down to it, if your design has brown and blue colors, your printed piece will too. But maybe the colors will be a little darker than you expected; Maybe the color shade didn't turn out exactly as you envisioned; Maybe the photograph will have more contrast than you saw.
The fact is: There are a lot of different models of computer monitors out there, and each one will have a variety of settings. My own monitor here has not just settings for brightness and contrast, but also for "tone", which will switch it between yellow, blue, and magenta tints.
Flat screens have proliferated because they are really incredibly space efficient, and easy to handle. However... they are just really not good when it comes to proofing images that will be printed.
What can the printer do? We can not come to your home and calibrate your computer. Instead, we can only warn you.
Just about every major online company has the warning- though you may have to dig to find it.
"Overnight Prints does not guarantee color will match the preview as it appears on a customer's monitor, as we cannot compensate for color variance on each customer's monitor."
"Are the colors on my proof exactly like my magnet or card? Because of the different settings on computer monitors, and the difference between computer colors and 4-color printed colors, the colors on your proof are not an exact representation of the colors to be printed on your magnet or card. "
95% of a printing company's customers will be happy with their printed design. Printed with quality machines, produced by quality designers, it's not as if the printed design is going to look bad. But... will see the occasional complaint from someone who felt that their photo print was too dark, and that is regrettable; It was someone who fell in love with their photo design as they saw it on a bright monitor.
Take this quote from Theoart at wordpress.com
"When it comes to prints being too dark, usually it is a result of an expectation of prints to appear exactly as they appear on a person’s monitor and not the printer itself. What this means is that the dark prints are really printing the way the image is but the users monitor is making a dark image look brighter. Being in the photo and fine art printing business, this is the one complaint that I hear the most.
This is most common for people using flat panel (LCD) monitors since they tend to emit brighter imagery than a more traditional and bulky computer (CRT) monitor. Laptops can be the worse culprit in all of this. MAC users may also experience this issue due to differences in the Gamma curve."
Is there a real solution to this issue? No.
But, I do have a trick for you. If you calibrate your monitor so that the last 3 dark colors in this band (below) are indistinguishably dark, and the light colors are clearly definable, you will have a better feel for how dark things will print.
It's not surefire- some printing companies will automatically adjust images in various ways to attempt compensating for how they expect most of their customer's computer monitors to be set. They might be adjusting their online proofs... and they might be adjusting the file that they are printing. (You didn't think shutterfly and other photo companies just printed your exact photo file, did you?).
Another tip: Laminated prints do usually look darker than matte prints.