What is the easiest and cheapest way to produce a coloured smoke?

Question

Preferably a brightly coloured smoke (red, orange, green, etc.) for finding leaks in pipes, duct work, etc. and tracing under ground burrows and leeds, etc.

Answer 1

Try an air conditioning supply house.

Answer 2

take equal amounts of sugar and salpeter, (buy some at a pharmacy) mix them together and melt over a dry heat. (like making toffee apples). whem the mixture dries and sets again you can light it up to make lots of smoke with almost no smell. I'm just not sure on how to colour it.

Answer 3

There are "smokers" that emit continuous wisps to find small air leaks. Plumbing specialty store.