Color - Blue

blue is:

• a hue color (chromatic)
• a pure color (without additive)
• one of the percepted human colors.
• is used as primary color:
  • coordinate in a colorspace (for instance the rgb colorspace)
  • in a rgb wheel
• located at 450 nm on the visual spectrum
• before violet on the visual spectrum
• after cyan on the visual spectrum
• one of the lowest wavelength on the visual spectrum (has therefore a lot of dispersion and this is why the sky is blue/violet)
• located at 240 degree in a rgb additive color wheel
• used mostly in a additive color model - ie with light (screen, monitor,…) and not with pigment (painting, printing, inking)
• coupled with this emotions: calm, trust, competence, peace, logic, reliability
• is a cool color

The complementary color of blue is yellow.