What does "being on the spectrum" mean?

[lolcow yoghurt]

The girl I've been talking with asked me if I'm "on the spectrum" or not. What does "spectrum" mean? Did she mean the electromagnetic spectrum? That's the only spectrum I know, so, should I answer accordingly?

Will she laugh at me if I mention the EMR spectrum or will she ask me my wavelength..?

 

[Neurotypical Mantis]

it's a hippie way of asking what your favorite color is

 

[Dunkin DoNUT]

She's asking about your melanin count. Are you at the extreme end of being pasty, or the other end that's bordering niggeredly?