Particulates in the air make for the effect, be they from forest fire, volcano, or just dust, simply put this is more of a problem in warmer air, dust from Africa can spread far around the planet, given for the most part just amazing red sunsets.
As was already said this is also seen in the recent issues between Indonesia and Malaysia and the fires burn in the former affecting the latter, causing a far stronger effect.
India is (in general) a warm and semi arid country making for a particulate problem add pollution to that as well and you get sky's that will be often 'not blue' although as a local I thought you would have noticed that the problem drops after the rains.
I would also have thought, that as a local you would know that Kolkata has had a building pollution problem for years.
https://en.wikipedia.org/wiki/Kolkata#Cl...
I think the main reason is the pollution, which can be very bad in India and in much of Asia. See the link about the Asian Brown Cloud below. Do you notice a seasonal difference with the monsoon? If the air is stable (no rainstorms), then pollution may be trapped near the ground, but if there is deep convection, like thunderstorms, then the pollution may mix vertically and skies will be clearer.
The sky may also be hazier and the less blue when a marine air mass is present, due to the large number of natural aerosols, like sea salt particles.
http://en.wikipedia.org/wiki/Asian_brown...
There is a chance of black or brown sky in areas where high pollution. In places such as high developed cities because of pollution from industries and pollution due to high population there will be concentration of gases such as CO, CO2 and methane high. This can cause change in sky color.
The pollution at an area can be understand from an indicator called licken. If licken is grow good in an area it shows low or no pollution.
Interesting question =) I would think that the colour of the sky has to do with the scattering of light and /or the angle of the overhead sun. I would have guessed pollution over your reference to climate though (clouds/over cast skies are not the colour of the sky in cold climates, so I am not sure what you mean)
Its pollution because India is as crazy as China to fuel its industrial obsession!
I live in India (Kolkata). But I noticed that Indian sky not so blue at first I think that cold climate country sky more blueish,but i realized that that's not true many hot climate countries like Dubai, Malaysia, Mauritius, the sky is also blue I want to know is that for pollution. and if it is not polluted it can also more blueish?
