I had an implantation bleed on the day my period was due, which was red spotting on one day and brown the next, and a BFP nine days later (I didn't test in the mean time so not sure if I would have got a BFP before that point).
I had an implantation bleed with my first pregnancy. It was around the day af was due. I then took a test a few days afterwards (about 5 days after af due) and got a very strong line after less than 1 minute.
For my first pregnancy I had an implantation bleed - really light - a couple of days before AF was due, then with this one I had just one spot of blood a week after AF was due and a week after I had a BFP. A friend of mine had her implantation bleed at 8 weeks pregnant and it lasted for 3 days, so it seems to be different for everyone!
I had an implantation bleed at 9 and 10 DPO (pink and only when I wiped), then got a very faint positive on a cheap test at 13DPO. Next day did another cheap test (a little darker) and also a clearblue digital (positive).