Unusual colored rain showered over Kerala, India in 2001. It was as red as blood rain. It did not happen once, but over three months.
I googled once. In the past, some people believe – war caused blood rain. When the blood has been spilled on the battlefield, it soaks into the ground. As the blood evaporates, (blood) vapors rise and condense into (blood) clouds. The (blood) clouds move over the land, and precipitation falls in the form of (blood) rain. Yes, from this myth perspective, blood rain is an indication of bad times – or even: deadfall. From another historical context point of view, people believes blood rain signals God’s anger, a warning against human sins. “God sent down this natural phenomenon on earth to remind us all to have faith (in God), to devote (God) and to think (in a very sharp religious manner) [“Ini peristiwa fenomena alam yang Allah turunkan di muka bumi untuk mengingatkan pada kita semua agar beriman, bertaqwa dan berfikir” – quoted from this site]
Anyway, it is (was) not blood, but still – it is (was) red. One of research answered: red-like-blood-color comes from spores of a locally prolific aerial algae from the Trentepohlia genus. Oh well, Trentepohlia spores can be red or green, and degrees of their dilution can make rainwater appear yellow or black. Although, however,
they still have unanswered question: How did so many local spores contaminate the rain? Another hypothesis was that dust had been picked up from the deserts on the Arabian Peninsula, mixing with the water in the atmosphere, and raining down upon Kerala as red rain. One more speculation came from CESS, that argue the particles had come from an exploding meteor, which would account for the loud sound and flash of light prior to the first occurrence of the red rain. The most controversy opinion came from one scientist who thought it was blood rain “the blood could have been sprayed as a waste product from a UFO that has extracted what they needed from the blood and disposed of it.”
Well, in November 2001, Tropical Botanical Garden and Research Institute and the Government of India’s Department of Science & Technology submitted the official report, stated that:
The color was found to be due to the presence of a large amount of spores of a lichen-forming alga belonging to the genus Trentepohlia. Field verification showed that the region had plenty of such lichens. Samples of lichen taken from Changanacherry, when cultured in an algal medium, also showed the presence of the same species of algae. Both samples (from rainwater and from trees) produced the same kind of algae, indicating that the spores seen in the rainwater most probably came from local sources.