There is a small, yet growing subfield within psychology called color psychology. Researchers in this field are interested in how people perceive, relate to, and respond to various colors.
Some of our reactions may be based on biology. For instance, since blood rushes to the face when one becomes aggressive, the color red, in both humans and animals, is a signal of dominance. Other reactions to colors may be based on learned associations. For instance, a Yankee fan may feel happy when seeing blue pinstripes because he or she associates that color scheme with the Yankees.
Toward the end of Parshat Shelach, we read about the mitzvah of tzitzit. We are commanded to place fringes on our garments, including a thread of techelet. The purpose of doing so is stated explicitly in the Torah: to remind us to follow G-d’s commandments and not wander after our hearts and eyes.
But how exactly does wearing white-and-techelet fringed garments remind us of the mitzvot and prevent us from wandering after our hearts and eyes? Rabbi Meir (Menachot 43b) tells us that techelet resembles the ocean, which resembles the sky, which resembles G-d’s throne of glory. Looking at techelet strings, therefore, reminds us of Hashem.
The Ramban adds that within the word techelet are the words kol (all) and tachlit (purpose). Meaning, at its core techelet reminds us of our mission in this world, which is to serve G-d by doing mitzvot and avoiding sinning.
Writing in the 15th century, Rabbi Isaac Arama suggests that another important moral significance is embedded within techelet. Medieval scholars assumed that seven colors flowed on a spectrum: white, yellow, red, green, blue, purple and black. At the extremes of the spectrum were white and black and sitting in the middle was green. Rabbi Arama (presumably understanding techelet to be green) argues that techelet symbolizes the middle ground between extremes, reminding us that all our character traits should follow the middle path.
If Rabbi Arama interpreted the message of techelet based on the color science of his time, perhaps we can interpret it based on modern color psychology. In a fascinating article on colors and marketing strategy, Lauren Labrecque and George Milne note that white, the total reflection of all colors, is associated with sincerity, purity, and peace. Blue, which (along with violet) represents the shortest wavelength of all of the colors, is associated with intelligence, trust, and duty. Colors on the longer end of the wavelength spectrum (like red, orange, and yellow), in contrast, stimulate states of excitement and arousal, oftentimes emotions related to sin.
Tzitzit are supposed to counteract sin. If we assume that techelet is blue, perhaps the duty and loyalty invoked by seeing blue and the purity invoked by seeing white are meant to counter sin, which is associated with red. In addition to the associations that lead us to think of G-d’s throne, the psychological symbolism of blue and white may serve to arrest the arousal of sin and remind us to be loyal to G-d.