The visual spectrum, for human beings, occupies only a very small section of the full electro-magnetic spectrum.
This, allows the possibility, that there are more possible colour qualia possible.
Of course, this is unimaginable. Or is it?
Though of course we have a very good theory of the full spectrum, such that we have infra-red cameras; all this in essence is doing is translating the infra-red phenomena laterally into the visible part of the spectrum. It doesn't tackle the fundamental question of other possible colour qualia. Or is there an argument that rules it out?
Nagel, in his paper, What is it like to be a Bat, launches into a defence of reducing consciousness to purely physical character. He suggests, according to Hacker, in a rebuttal of Nagels thesis, Is there anything it is like to be a bat that the qualitative character of other species experience may be beyond our capacity to conceive.
Of course bats are famous for using echo-location to navigate space; and one might ask how this feels or sensed or understood as qualia. But human echo-location is possible, and this without any external equipment. One might suppose, tht given the species affinity we have with bats - we are both mammals - to understand how it feels to echo-locate, is perhaps to gain some glimpse in the bat-world.
Of course, given echo-location by actual instrumentation, this would be very different, we would see our environments; a visual representation would be put before our eyes.