Implantation??? (no pic)

Is implantation bleeding always pink? Or can it be light brown? I normally have light brown for two or three days before my period really kicks in, but this cycle it didn't happen. I was supposed to start the 13th. Didn't happen. All tests negative. Day before yesterday, I wiped and it was light brown like I was hitting those pre period days. Only it was just that once! Could it be implantation? I already know I probably ovulated later than what I initially thought since my cycle is off (not unusual). What do you ladies think?