Bleeding

During my entire 2 months and a couple days on the depo shot I've never had a regular red period, they were always brown and would last a week or more. Well I'm due for my next shot on the 29th but I won't be going back to get it. I just got done with my (brown) period and a few hours later it comes back but now its bright red. Is it because I'm due for the next one? Or because I'm taking Geritol?