Just use an event running on parallel process, have it set a variable to character's map Y, and break up the stages of tint like so:
@> Control Variables: [0002:PlayersY] = Player's Map Y
@> Conditional Branch: Variable [0002:PlayersY] == # (whatever to map Y is you want the tint to change at)
@>Tint Screen (0,0,0,0), @60
@>
: Else
@>
: Branch End
Then just copy the Conditional Branch as many times as you want to change your tint.