The semi-official definition of orange noise is "a quasi-stationary noise with a finite power spectrum with a finite number of small bands of zero energy dispersed throughout a continuous spectrum." We have not been able to determine where this definition originated but it is commonly used in reference material.
Orange noise relates to musical scales. The bands of zero energy coincide with the notes in the scale. In effect this means that the in-tune notes of a scale are removed, leaving only the out-of-tune frequencies. This creates a clashing, displeasing noise.
Main page: Noise Colours