Perhaps in addition to generating X-rays, Superman can also generate microwaves, and the two functions are closely inter-related.
This is actually an interesting explanation for how the Martian Manhunter's "Martian-Vision" works, posited by Mark Waid in his YEAR ONE miniseries: the Martian Manhunter describes his eye beams as being "microwave" beams; he was, in that miniseries, able to "bake" clayface and cause a road to become sticky by exciting the molecules inside of it with his eyebeams.
This is logical, considering it doesn't make sense that the Martian Manhunter, whose weakness is flame, would have the ability to project flame-causing heat beams (does Superman have Kryptonite Vision? NO!)
Though it may be an artistic choice made on a color that looks cool, note that in Morrison's JLA, when the White Martians and the Martian Manhunter use their "Martian-Vision," it is a deep purple that is almost like blacklight. Could it be that they were trying to imply that Martian-Vision is actually based on projection of the ultraviolet? This would also be an interesting power.