GrafiLite - Why viewing conditions matter
Assessing a print under  artificial light and in the wrong ambient conditions can cause you to see the colours in the image incorrectly. Illumination temperature (°k) and quality (CRI) affect the actual colour you see. This can range from a neutral grey or skin tone looking warmer or cooler under different lighting, to a pair of colours appearing identical under one illumination and considerably different to each other under another.

This phenomenon is knows as metamerism. Even in everyday life we can see the problems metamerism causes; for example, a pair of items appearing to match under shop lighting, but not when viewed in daylight. Daylight is evenly balanced across the visual spectrum, meaning it has equal levels of red, orange, yellow, green, blue, indigo and violet ‘energy’. Artificial light does not have this; therefore colours are rendered more accurately in daylight.