The term blue may refer to any of a number of similar colours. The sensation of blue is evoked by light having a spectrum dominated by energy in the wavelength range of about 440–490 nm.
Blue is considered to be one of the three primary additive colours in the RGB system; blue light has the shortest wavelength range of the three additive primary colours. The English language commonly uses "blue" to refer to any colour from navy blue to cyan.
The complementary colour of blue in colour science is yellow (on the HSV colour wheel), while in art the complementary colour to blue is considered to be orange (based on the Munsell colour wheel).