It happened the day of with my first lasted about 20 min then went away

No This is the day of

And usually comes before period is due

Implantation is normally old blood cause it take a while to leave the body

It sounds like implantation to me

Did you miss your period

Dark blood means it old

Im getting that off and on

It could be implantation

Pink..dark blood is old blood

This isn't implantation then I've got some red pink brown and black

Spotting