first, using soap will remove some of the built up non stick coating, so never use soap on a cast iron pan. scrape off big chunks of food with a plastic or wood spatula; scrub the pan smooth with a plastic scrub pad or a stiff brush (not metal, not Brillo, not SOS). use hot water with the last step. dry the pan on medium-low heat. if the pan isn't perfectly smooth at this point, use a folded up pad of paper towel, some kosher salt and olive oil to scrub the still warm pan. wipe out the pan, leaving a sheen of oil, and let the pan cool. now it's clean and ready for storage.
when cooking bacon, it's fine to put bacon in the cold pan. the bacon will stick at first, but as the pan gets hot it will release. if after some of the oil is rendered it's still sticking loosen it with your spatula. btw, frying bacon in your skillet like you were doing is one of the best ways to season it and build up the gleaming black, non-stick coating that makes cast iron pans so beautiful.
the discoloration or uneven coloring you are seeing is probably the result of using soap. keep frying bacon, eggs, steaks, stir frys, sausage--anything where there is oil--and follow the process for cleaning and seasoning it and all that will be a distant memory very soon. (i don't do tomato sauce in my cast iron pans, and i don't do a lot of boiling in them. that's just me.)
the most wonderful thing about cast iron pans is that they are nearly indestructible. just don't drop them--they may shatter. and store them in a dry place so they don't rust.
good luck with your first cast iron pan!