[Konstantinos]

In OnPlayerDisconnect callback, get player's color

pawn Код:

GetPlayerColor(playerid)

and save it to your already existed register/login system. In OnPlayerConnect callback, let them login and then

pawn Код:

SetPlayerColor(playerid, load_the_color_and_set_it);

PS: I never had problems like resetting my color on player's death.