
The study included 28 healthy participants (22 males and 6 females) ranging between the age of 20 and 67 years (28.6 ± 11.3 years). Considering the above, the purpose of the current study was to evaluate urine color during different hydration states, with the results expressed in CIE L *a *b * color space. The L *a *b * color space model is only accurately represented in three-dimensional space. a * and b * are color directions: –a * is the green axis, +a * is the red axis, –b * is the blue axis, and +b * is the yellow axis.

In the L *a *b * color space, L * indicates lightness ranging from 100 (white) to 0 (black), while a * and b * indicate chromaticity. In recent years, tristimulus colorimetry developed by the International Commission on Illumination (CIE L *a *b *) has been widely adopted as the reference method for color analysis. Traditionally, urine color has been measured using a subjective color scale. Urine color has been shown to be a viable marker of hydration status in healthy adults. School of Exercise and Nutritional Sciences, San Diego State University, San Diego, CA, United States.
