Icon intended for bad anatomy, but close enough
So. Many. Things. Wrong.
Basically color is determined by two thing: the wavelength of light after it has been reflected off the object, depending on properties of the object's surface and the environment around it, and the way that the eye and brain perceive them. To say that the color red, or any color, can hurt even the most alien body is ridiculous for the simple reason that red doesn't exist unless you see it.
Now, it's remotely possible that what the aliens mean is that they are hurt by the particular wavelength of light that humans generally perceive to be red, however, A: That's a pretty damn specific range of wavelengths. B: This could be solved by a very simple filter on the eyeholes of their space suits. C: Any device that could render the red in the area green would either affect the object directly, in which case it would be impossible to reverse without turning all green objects red whether they were originally red or green, or would affect the light coming from objects, in which case its effects would disappear as soon as it was removed. D: In the latter case, how such a device could -only- affect red and not accidentally shift infrared radiation into the range of visible red light is entirely beyond me. E: There are simply no words regarding the sponge. No words. None. F: Still stuck on the sponge. No words. G: G would have been objecting to the way the aliens chose to explain their "weakness", but this can be explained away by them knowing humans are stupid and so talking down to them. Like how you might tell a child not to touch a stove, or it will bite them. H: I cannot conceive of an environment in which a species could evolve such a weakness and not die off long before discovering space travel. Short of them being genetically engineered by the universe's biggest dick, that's pretty remarkable all on its own.