This post is in response to a reader question (thanks Christine).

Color is an event that occurs among three participants, lightsource, object and observer. It should therefor come as no surprise that one and the same object will look different under differing lichtsources. Your clothes do not have the same color under a fluorescent tube, a regular light bulb or in sunlight. However, most of the differences are 'corrected' in our brain by a fascinating psychological process called 'color constancy'.
For today, however, I'll focus on another interesting subject related to lighting: Metamerism.

A color is always composed of light of different wavelengths. Sunlight, for instance, can be deconstructed to the colours of the rainbow. But also a surface can be deconstructed in a spectral analysis.

This is the spectral analysis of a certain shade of red:
This is the spectral analysis of almost exactly the same color red:
There's something peculiar about these two colors: they are metamere. Which means that perceived in a certain light, in this example sunlight, they will appear exactly the same to our eyes. But under another source of light, say an electric bulb, they will appear different.
Metamerism is a quite common phenomenon that can cause problems in color schemes. If, for instance, the same color is ordered from different manufacturers, there's a distinct possibility that they will be metamer. Which means they will not be the same in all circumstances. This is because different manufacturers use different pigments. Metamerism is something to keep in mind when trying to match two colors. You should therfor make sure to match the colors under the proper lightsource. If you're trying to match colors for the facade of your house you should evaluate them in sunlight. If you're comparing two colors for interior use, match them under the kind of light you're planning to use in your room. If the colors will be utilised in differing circumstances (clothes come to mind) all bets are off...