Perceptual Issues with Color
Last updated
Last updated
This refers to the inability to perceive certain colors. It is caused due to missing or defective photoreceptors (mainly referring to the 3 different kinds of cones). The lack of different photoreceptors cause different kinds of color blindness.
About 10% of men and 1% of women are color blind. The most common color blindness types are the ones caused by the lack of M and L wavelength cones. This makes it hard for color blind people to distinguish between red and green.
While designing visualizations, we must try to keep the following in mind, with regard to color blindness:
Use color-blind safe palettes
Use blue/orange or blue/red palettes
Consider using variations in color intensity or saturation
Test the design with color blindness simulators
The size of components in a graph will have a big impact on the way colors are perceived. For example, in a scatter plot, using small dots will make it difficult to distinguish between colors; making the dots larger will make it easier to distinguish between colors.
A rule of thumb is to use high saturation in small areas and low saturation in large areas.
Contrast is the difference in luminance or color that makes objects distinguishable.
Visualizations are often organized in layers, so contrast must be used appropriately.
Layers may include background and foreground objects etc. Contrast can be used to separate the layers.
Luminance is the most powerful channel to create contrast between objects.
The background has an impact on the way the foreground colors are perceived, especially if the foreground contains symbols that use luminance-based color ramps.
Color Constancy is the idea that the same color is perceived differently in different backgrounds or surroundings. Consider the following two grey bars (same hue):
If we use different backgrounds, the same bars will be perceived differently:
