Bright red instead of orange and blue instead of purple

Color reproduction in print is very challenging.  The paper you print on makes a huge difference in how color is perceived.

The first thing to keep in mind is that not everyone sees color in the same way.  Yes, our bodies and minds react in similar fashion, but what is dark green to me may be more of a brownish green to you.

The printing industry has tried to take the personal interpretation out of color by using mechanical devices to read color bars on the printed product and in newspapers, a grey bar functions as a uniform standard to set ink levels.  The grey bar pictured below (at the bottom of a newspaper page) allows the press operators to see that the three color inks they use, Cyan, Magenta and Yellow are balanced correctly. 

If you have ever mixed paint you probably know that if you mix yellow and blue paint you get green - it is a similar process for a grey bar.  There is a certain percentage for each of these colors, that when they are mixed together they make grey.  If the grey bar looks red, pink, blue, or yellow they know they need to adjust their ink levels.  The entire page uses the same exact ink source, so if you control your grey bar you control your color.

The first step to make your colors accurate is to make sure the ink is put on the paper correctly.

Next, you can examine how the color was "made" in prepress - or on the computer now days.

I mentioned earlier that if you want to make green, you use yellow and blue.  There is no way to make a brown color only using yellow and blue, so if the green looks dark, "muddy" or brown, there is another ink in that mix.

Red and a blue are difficult colors to reproduce using four color process. 

The three colors Cyan, Magenta and Yellow are combined with black in four color process to create full color photos and artwork.  If the color mix of the red includes cyan or black, it won't be a bright red.  If the yellow is more than 85% strength, the red will look orange unless the press operator turns up the magenta more than he should, or the yellow down more than he should.  The mix on bright red is critical for a good color reproduction. 

A vibrant blue is similar, you need a mix of cyan and magenta, however if the magenta is more than 30-35% the blue will begin to turn purple.  If black is added the blue turns dull and dark.

You should always keep in mind that staring at the same color for very long actually stresses the muscles and sensors in your eyes and color shifts can happen.  It does not really happen on the paper, but in our perception of color.

The examples below illustrate the physical impact of continuing to look at the same colors/images.

In the first image you see a black and white version of a mug shot.  If you stare at the mug shot without looking away for 15-30 seconds and then close your eyes.  (It may help to cover your eyes with your hands in a bright environment)  You will "magically" see the reverse image on your eyelids.  These are your color receptors being tired and creating the reverse image as a result.  You can make the effect more pronounced by staring longer than 30 seconds.

You may want to click on the photo and enlarge it to help the process.

Color impacts our eyes in the same way.  Here are two negative color images for you to experiment with.  Stare at the dot/dots on their nose without looking around for 15-30 seconds and then close your eyes.  You should see the natural color image after a few seconds on your eyelids.  You can stare longer to increase the reaction. 

Color is truly subjective and can be impacted by many factors including ink levels, ink mixes and light.

Light has different variations of color.  You don't notice tremendously, but sunlight is bright white, fluorescent bulbs produce a greenish light while some light bulbs create a yellow hue. 

You should try looking at a printed page in these different types of light and see the color variation.  The ink doesn't change, the ink mix doesn't change, just the color of the light.

We see because light bounces off the paper and reflects back into our eyes, so the color of light has an impact on what colors we see.

I typically cringe when my wife asks me if something is very dark blue or if it is black because I know when she goes outside in the bright sunlight I am typically wrong!  So beware about being adamant about what color something is, it might not be that color to everyone.