The relationship between color and psychological state is well-established in environmental psychology. The colors in your immediate visual field — including your desktop wallpaper, which you see for cumulative hours each day — have measurable effects on arousal levels, mood, and cognitive performance.
Blue is the most consistently studied color in productivity contexts. Environments dominated by blue tones are associated with improved creative performance and sustained concentration. Blue occupies a large wavelength range and is found extensively in natural environments (sky, water), which may explain the evolutionary associations with calmness and stability. Blue-toned wallpapers — deep ocean photography, twilight skies, abstract blue gradients — are the safest choice for a general work environment.
Green has strong associations with rest and recovery. This is well-established enough that hospital recovery rooms and mental health facilities frequently use green environments by design. For a workspace where you experience significant stress, green wallpapers may provide a mild calming effect during the accumulated hours of peripheral visual exposure.
Red and orange tones are associated with increased arousal, faster decision-making, and higher alertness. For work that benefits from energy and urgency, warm-toned wallpapers might be appropriate. For detailed analytical work where sustained calm focus is required, warm tones are usually counterproductive.
Dark, desaturated palettes (which dominate the premium desktop aesthetics community) have a practical basis beyond aesthetics: low-saturation, dark backgrounds reduce visual fatigue during long computing sessions by decreasing the overall brightness load on the display.
Practical recommendation: maintain two wallpaper presets — one energizing for morning hours, one calming for afternoon focused work periods. Most operating systems support automated wallpaper changes by time of day.