Why are few bottles green or brown in color ?

Assertion: Brown algae vary from olive green to brown in colour. Reason: Fucoxanthin is responsible for color variation in brown algae

Pure HI kept in a bottle axquires a brown colour after sometime. Why? (b) Ferric ioddic is very unstable but ferric chloride is stable. Why? (c ) KHF_(2) is well known but KHCl_(2) and KHBr_(2) do not exist. Why?

Why are water droplets are seen on the outer surface of a cold drink bottle?

Why are algae green ?

Why juice bottles are placed under water in the cold countries ?