Genetics, light and shadow, the color and texture of the stream bed, the clarity of the water, the riparian vegetation, the age of the trout and the time of year all figure into a complex equation whose end product is a trout. Each is unique. Some of the trout have pale pink sides, some almost orange. Some have red-gold flanks and bright red gill covers, particularly when in spawning dress. Smaller fish often have iridescent blue green parr marks.
Older trout are sometimes an almost uniform olive brown.
Fish from cloudy streams tend to silver and lack the bright colors of those living in clear waters.