Color bleed is an undesirable artifact that appears on some displays causing discolored stripes to appear on the screen both vertically and horizontally. Essentially, large elements (either uniform in color or with a very fine grid) that are being displayed have a faint "ghosting" that extends past their boundaries across other parts of the screen.
When it matters
While color bleed isn't apparent with every type of content, it can be an issue with the majority of usages for PC monitors. It is not uncommon for modern user interfaces to incorporate single color flat elements, which is exactly the type of content where color bleed can appear.
To accurately measure the amount of color bleed that appears on monitors, we developed a test sequence with large blocks of primary colors, secondary colors and white, arranged in a row and column over a gray background. With the test pattern shown on screen, we place a Colorimetry Research CR-100 colorimeter aimed at the center of the screen and take a measurement of the grey area beside the pattern.
After each measurement, the pattern shifts to change the color aligned with the colorimeter's measurement area to consistently measure the amount of bleed that appears. We then measure a pure grey slide as a control and calculate the average variance both horizontally and vertically (Color dE).
Pixel Row Error
The pixel row error test represents the amount of color variance that appears in the area surrounding our test pattern horizontally. They usually look like faint bands that spread across the entire screen on either side of the image.
Pixel Column Error
The pixel column error test is equivalent to the previous test but it evaluates color variance of areas above and below the pattern instead of the sides. The pattern is also rotated to better enable the effect.
How to get the best results
Unfortunately, color bleed tends to be an inherent property of the screen itself, so little can be done to reduce its appearance. We are not currently aware of methods to reduce its effects, so if this is an issue you feel might be problematic for your use-case, it is best to pick a monitor free of it when shopping.
Color bleed is an effect that appears on some monitors where colors seem to extend past the element they are supposed to be in and shade over the rest of what is shown on-screen. Not much can be done to limit its appearance except limit the amount of large uniform elements displayed on-screen. It is not an issue on most monitors, as even those that do show some bleed don't have an amount significant enough to be distracting.