Light has different biological effects depending on the color temperature and intensity. This may be the reason for its differing effects. We investigated the influence of color temperature (3000 K, 4500 K, 6000 K) under constant high intensity (1000 Lux) on concentration and creativity of 50 students and employees of the Cologne University of Applied Sciences, Campus Gummersbach (age: 30.9 +/- 10.8y.). As test method we used d2-bq-test, creativity test (mean of the number of ideas on 5 themes), word test and logic test. In addition, test subjects were asked to evaluate their impression of light by means of a questionnaire. To exclude the circadian influence and learning effects on the result, we performed tests at the same time of the day using a random order of color temperature. We found that creativity was better under warm light (3000 K) than under colder light (4500 K, 6000 K). Concentration was best under cold light (6000 K). Under the same light intensity conditions, subjects judged blue light (6000 K) to be brighter than red light (3000 K).