Dark Brown period to Bright Red period

So my period started Monday, it was a very dark brown, I was told it’s old blood but now after 3 days of that I’m starting to bleed red(normal) period. Does this mean my period will be prolonged or does it mean that the brown period blood wasn’t actually my period and the red period blood will still be my actual period and I’ll have to deal with it for another 4/5 days?