An octave is a doubling of frequency. 400 to 800 THz is one octave. Color has one octave.
The way you know that is you don’t experience redness when absorbing ultraviolet light, and you don’t experience blueness when absorbing inferred light.
It doesn’t “loop around” like the A note does at 440 Hz, 880 Hz, etc.
An octave is when a doubling of frequency leads to a new waveform that stimulates the same set of neurons as the frequency an octave below it.