I am on my third pack of birth control, and today I noticed I was spotting brown colored blood. What does this mean?

First of all what pill is it? if it is a 28 day cycle pill and you are only 3 months in , it is normal and it is brown because it is old blood, your body is getting used to the pill. If it is a continuos cycle pill, meaning it is either seasonique or seasonal which causes you to have only 4 periods a year or stop them altogether than this is the breaking in time, and it will go away soon again it is normal esspecially if you just started these pills, and again the brown color just means it is old blood, don't worry unless it is bright red and clumpy then I would go to the doctor and get a pelvic done.