Blue dye test positive.

Hi ☺️ So I have been feeling like I’m pregnant for a few days but my period isn’t due until the 25th. Today, 3 days before my period I took a test. Blue dye which now that I’m doing my research, I see is a mistake. I started the day spotting old, dark brown blood and not very heavy, which is very unusual for me since my periods are very regular and start off heavy and are heavy from start to finish. I took a blue dye test and watched it. Before the 10 minute mark was up, there was a line that most definitely did not look like an evap line because it has a blue color. I’m still spotting a little and now I’m kind of suspicious. Could this be a false positive? How likely is it on a blue dye test?