Everyone perceives color slightly differently. There are all sorts of variables, and the colors that you perceive this morning might not be the same as if you came back to the same image in the afternoon. Things like mood, tiredness, and stress can all play a role, as well as more deep-seated biological and neurological traits.
Another important factor is colorblindness. Because nearly 9 percent of the population has some form of colorblindness, statistically a good portion of the people who look at your photos or graphic designs will see the colors quite differently to how you see them.
There are two main types of colorblindness. The vast majority of those with colorblindness can still see colors--they just have trouble distinguishing between some of those colors. The most common types are deuteranopia and protanopia, which are characterized by trouble distinguishing between middle- and long-wavelength colors like green and red. Less common is a type known as tritanopia, where it's hard to distinguish between shorter wavelength colors like green and blue.
Those with Protanopia-type have trouble with long wavelength colors such as red and orange and green and therefore have trouble distinguishing between green and red.
In some cases, you might be able to compose the shot specifically to factor in colorblindness. That's relatively straightforward when creating a graphic design, but it might also influence the background you choose when doing a product shoot in a studio or the clothes ensemble on a model. But even if you can't change the scene, such as with landscape photography--it can still be useful and interesting to see how nearly 10 percent of your image's viewers will perceive the colors in it.
Simulating Colorblindness in Photoshop
Photoshop has a built-in feature that can simulate what they'll see.
This tool is especially useful for graphic designers to make sure that designs are clear to the maximum number of people, but whether it's just out of curiosity or whether it's structuring the colors of a commercial advertising shoot, the tool can also be useful for photographers to get a sense of how different people are likely to perceive your image in terms of its colors.
It's very easy to do. And it does not affect the underlying image--think of it as a removable preview filter.
Open your image as you normally would.
Then go to View > Proof Setup. You have two choices: Protanopia-type or Deuteranopia-type. The effects are similar but not quite the same.
Here are some practical examples:
[caption id="attachment_21698" align="aligncenter" width="678"] Protanopia-type[/caption]
[caption id="attachment_21703" align="aligncenter" width="678"] Deuteranopia-type[/caption]
[caption id="attachment_21690" align="aligncenter" width="678"] Protanopia-type[/caption]
[caption id="attachment_21692" align="aligncenter" width="678"] Deuteranopia-type[/caption]
[caption id="attachment_21705" align="aligncenter" width="678"] Protanopia-type[/caption]
[caption id="attachment_21700" align="aligncenter" width="678"] Deuteranopia-type[/caption]
[caption id="attachment_21708" align="aligncenter" width="678"] Protanopia-type[/caption]
Simulating Colorblindness Without Photoshop
If you don't use Photoshop or want to dive a bit deeper into the other forms of color vision deficiency, color-blindness.com has a free color blindness simulator that you can upload your own photo to.