Understanding how the human eye perceives light is an important concept in Design. Color is not perceptible without light and how we perceive color is influenced by physics and lighting atmosphere. Different sources of light will create different color results. Take a tree for example. In a simplified view, a tree is made up of green leaves and brown bark, but looked at in the morning compared to mid day, the perception of the color differs because of the change of intensity of the sunlight and other atmospheric changes. This phenomena is known as Metamarism.
Metamarism is the visual phenomenon of an object appearing to have changes in color due to variances in the source of light. This is an important design concept to remember! Each light source is unique, and chosen colors will look very different with even the slightest change in light.
When considering digital or print design, the way your website or printed brochure appears to the consumer is largely dependent on their monitor, office lighting, and where they are viewing the brochure (indoors, outdoors, etc.).
These paintings by Claude Monet are the same cathedral at different times of day. This is Metamarism at work.