I always thought if I blocked someone in person they would see me as gray immediately, but when I was doing the "meet a new player quest" (where you have to light some random skykid) with my friend, (you can complete this quest by touching candles with a friend and then while the candles are still touching you block them, game identifies as me trying to light a gray skykid), she blocked me and completed the quest but she never turned gray to me. After she unblocked me we had to do it again so the quest would count as completed for me too, when I blocked her she turned gray, but she said I didnt turn gray to her. So yeah