Temporal veins are common and do not cause migraine headaches. Straining your temporal muscles because you have migraine headaches can cause more engorgement of temporal veins and that is why you are noticing them.
In a study done at out practice on over 40 patients whose blue temple veins had been treated, that was never reported. The cause of migraines is very complex, but it is typically based on arterial spasm initially, not from superficial veins on the face.
Removing blue temporal veins will not affect migraine headaches in any way. These veins can be treated safely in many ways.