The Sirocco is a wind that blows over Italy, from the Sahara, to the Alps. It brings red dusty air from the desert. I have been driving in the Moroccan part of the Sahara, many years ago, and I remember that, contrary to the sand found on a beach, the desert is sand, but also much very light dust.
When the Sirocco meets for example moist air from the Atlantic, it causes reddish rain and, if it is below freezing point, reddish snow. It is not only the case near the Alps but also on the Cape Verde islands, the Canary islands, and the Mediterranean coast of Spain, all of the above, places that I have visited and experienced such "red rain."
Was it a very strong case of red snow in the Alps in 1955? I don't know, I was only 7 years old at the time. I tried to google it in both English and French, which is my mother tongue but to no avail.
The bottom line: It could have been a case of "red snow" in the Alps in 1955 as it is not so unusual, but I find no record of it.