Why My Printer Printing a Totally different Color?

"Why didn't the color on my print out come out like the color on the computer screen?"  

Pulling my hair out because the beautiful layout for booklet cover is not printing correctly. The nice collage of images behind title unified into the same color of purple with a hue/saturation adjustment layer prints pink on clients printer. Well pinks not so far from purple, I thought maybe its just her printer settings. But it print GREEN on my printer. Now thats totally different from purple! 

I thought maybe I just need to print from flatten image. One Article suggested using PDF as my output. I tried JPG and PDF with same results.
Then I discovered a whole new concept with respect to printing that I had never encountered publishing websites -- of color management.

When working with digital images, we use color models to describe these colors.  There are a number of them: RGB, CMYK, Lab, etc., and each of them uses a different way of describing colors.  In the various color models, there are color options known as color spaces. For instance, RGB, contains sRGB, Adobe RGB, Apple RGB, etc. The CMYK model also has various color spaces to work in.  These spaces have a limited range of reproducible colors. This range of colors is known as gamut. 

The various devices work within their own limited color gamut. To make things even worse, no two devices have the same color space. Although they all use RGB to define color, they interpret it differently.

When using Photoshop (or other image-producing software), image color values are actually being adjusting numerically. These numerical values are not really colors at all. They only have a very localized color meaning in the color space (gamut) of the device that is reproducing the color.

So whenever your image is moved from one device space to another device with a different color space (i.e., scanner-> monitor-> printer), which can only reproduce colors in its gamut, the image colors will change (i.e., pretty blue on screen, dark purple in print). The color change happens because each device has mathematically interpreted the RGB or CMYK values according to its own color space (gamut).

Because each device has a different color space, it’s impossible for all the colors you see on your monitor (RGB color space) to match the output from your desktop printer (CMYK color space). Their gamuts are different.

Using a color management system is one good way to help achieve something close to consistent and predictable color between devices.  Luckily Photoshop has a very good color management system built into it. 

Items to consider to ensure what you see on the screen is what you get in your print (WYSIWYP). Calibrate your monitor, Color Settings, printer drivers to set monitor color space to printer's, paper profiles (used paper's recommended by printer) See rest of this article for detailed steps »

Most important but overlooked step: Change Your Photoshop Work Space Color Settings


1. Edit > Drag down to Color Settings > Advanced Options


2. Working Space Setting - RGB > Click the Adobe RGB from default sRGB 

Adobe RGB (1998)
Is the largest recommended RGB working space and suited for print production with a broad range of colors.

sRGB
Is designed to reflect the characteristics of the average PC monitor. sRGB is suitable for RGB images destined for the Web, but it is not recommended for print production work

 3. Do not change the remaining Working Spaces Settings. 

    Conversion Options  Engine: Use the Adobe ACE (default)

In the end when she took it to a professional designer's printer, the document's colors printed perfectly. No doubt she has her software and device settings all set for color print output.

In general, you will be working in RGB throughout the printing process. While color printers inks are actually CMYK, they are expecting RGB images to come through them.  The conversion takes place in the printer and your software.  Sometimes when working on images that will be sent to a publisher, you will need to convert your image to the limited CMYK gamut.  You can preview any color changes using Soft Proof in CMYK mode and turning on Gamut Warning. All of these options are available in the View Menu. 

In Photoshop you can use Gamut Warning in a number of ways to adjust problem areas. 
Duplicate the original image for gamut correction! 
Save as the duplicates name-proof type in case you need to print again. (eg. Filename-CMYK.psd).