Asthenopia, or eye strain, describes symptoms that are many and varied, including eye pain, double vision, blurred vision, headaches, or fatigue. Any task that requires your eyes to focus for a long time can cause eye strain, but the top offenders are the extended use of phone or computer screens or reading, particularly in the dark.

The Golden Gate Bridge was originally meant to be painted in blue and yellow stripes to increase its visibility. The iconic red color was only the primer. However, after seeing the bridge painted in this red color, a color that has since been officially called international orange, the consulting architect decided that it was more pleasing to the eye and left it as it was.

Fast food chains have figured out that the combination of red and yellow makes people hungry. McDonalds is the primary example of these colors being used. Since it's so commonly used, people now associate those colors with food.