When do you count the first day of your period as?

Mia

Hello, I am ttc and want to be sure I'm getting an accurate timing of my cycles. According to glow I should start my period tomorrow but was obviously hoping it wouldnt come. I just went to the bathroom and the tissue was very lightly tinted pale pink. My question is do I count this as the first day of my period or do I wait until it's full on actual bleeding to count as day 1? Thank you!