What is the blue discharge coming from my propane hot water tank's vent?

Crud is coming out around the seems of the hot water tank's vent. Some of it is black and gooey which I ume is creosote from from the chimney's previous use. There is also white chalky stuff which appears to be some type of mineral. I put paper toweling on the floor under the vent pipe to catch this stuff and I now see there is a blue ring that formed on the toweling. None of these three things have an odor What are these things coming from and what are they?