A red sunset means that the next day is going to be quite pleasant. There is a saying that goes, red sky at night shepherd's delight, red sky in the morning, shepherd's warning.

If the sky is red at night it's going to be a calm day BUT if there is a red sky in the morning it's going to be stormy or rainy.

Refer to: http://www.phrases.org.uk/meanings/red-sky-at-night.html

sailors heed warning - stormy whether coming. red sky at night - sailors delight!

It comes from an expression: Red sky at night, sailor's delight; red sky at morning, sailors take warning. Nautical folklore holds that a red sky in the morning portends bad weather.