I was, which is why I did not mention fair hair.
At the time of his conquests of these areas, Alexander's armies did not have a very large Greek contingent any more - his invasion of India was undertaken with a force consisting almost entirely of Asian-born troops.
Hence the carping about how he had "gone native" with his Persian dress, Asian troops, Bactrian wife, etc.
I don't buy into the theory that Alexander's Greek troops had a significant impact on the gene pool - there were many more of Alexander's troops stationed in Egypt than there were in India and Egyptians don't look like Punjabis.
Following Alexanders demise, during the Diadoch and Roman time, the people (at least the upper class) certainly had a strong Greek influence. But anyway, todays Egyptians are to the vast majority descendants of the invading Arabs.
I don't buy into the theory that Alexander's Greek troops had a significant impact on the gene pool
I'm ambivalent on this. The Graeco-Baktrian Kingdom in the Punjab region, following Alexander, had an evidently greek culture. Artworks show European features. There had to be Greeks among them, at least at the top. Today, as you said, there are people with bright eyes, light complexion and fair hair. I won't totally rule out an influence by Greeks in the region.
However your position is being corrobated by the fact that the Mazanderani and Gilaki people (North-Iranians living at the south coast of the Caspian) who are natives and had little intercourse with other people, have lighter complexion, eyes and hair.
Prominent example of a Mazanderani is the Ali Larijani, the Iranian regime's nuke negotiator:
I have always wondered if Alexanders uncle, acting as ruler of Macedon in his absence, sent significant Macedonian reinforcements or whether he kept those troops home to dominate Greek & Balkan territories. There should be some indication you would think.
Either way, Alexander left signicant garrisons at strategic points along his route of march. One would think that the further East he got, the fewer actual Macedonian’s would populate those garrisons.