String[] team = { "Marviin", "Spieler2", "Spieler3"};
for(String member : team) {
     String rank;
     if(member.equals("Marviin"))
          rank = ChatColor.DARK_RED + "Owner";
     else
          rank = ChatColor.DARK_RED + "Admin";

     if(Bukkit.getOfflinePlayer(member).isOnline())
          sender.sendMessage(rank + ChatColor.YELLOW + member);
     else
          sender.sendMessage(rank + ChatColor.DARK_GRAY + member);
​}