Any of several southeast Asian evergreen trees of the genus Citrus, widely cultivated in warm regions and having fragrant white flowers and round fruit with a yellowish or reddish rind and a sectioned, pulpy interior, especially C. sinensis, the sweet orange, and C. aurantium, the Seville or sour orange.
The hue of that portion of the visible spectrum lying between red and yellow, evoked in the human observer by radiant energy with wavelengths of approximately 590 to 630 nanometers; any of a group of colors between red and yellow in hue, of medium lightness and moderate saturation.