Theoretically, it can be a single point regarding the reference unit (here, the colour). Consider ideal laserlight for example, there you have just one specific wavelength, i.e., a single colour. The magnitude might differ, but it would be a single point in a mathematical sense.
As an engineer, I concur.
Although I would make one adjustment:
Theoretically, it can be a single point regarding the reference unit (here, the colour). Consider ideal laserlight for example, there you have just one specific wavelength, i.e., a single colour. The magnitude might differ, but it would be a single point in a mathematical sense.