I'm confused at this error, please help me

        RelationshipManager.PlayerTeam BlueTeam = new RelationshipManager.PlayerTeam();
        RelationshipManager.PlayerTeam RedTeam = new RelationshipManager.PlayerTeam(); 

[ChatCommand("play")]
        private void PickTeam()
        {
            BasePlayer player = new BasePlayer();

            List<RelationshipManager.PlayerTeam> teams = new List<RelationshipManager.PlayerTeam>();
            teams.Add(BlueTeam);
            teams.Add(RedTeam);

            int RandFloat = UnityEngine.Random.Range(1, 2);

            RelationshipManager.PlayerTeam RandomTeam = teams[RandFloat];
            Puts(RandomTeam.ToString());
            //RandomTeam.AddPlayer(player);
            if (RandomTeam == BlueTeam)
            {
                //string randomTeamColor = $"<color=blue>Blue Team</color>";
                //SendMessage($"You have been placed into team {randomTeamColor}");
                Puts("BLue Team");
                RandomTeam.AddPlayer(player);
                return;
            }
            if (RandomTeam == RedTeam)
            {
                // string randomTeamColor = $"<color=red>Red Team</color>";
                // SendMessage($"You have been placed into team {randomTeamColor}");
                RandomTeam.AddPlayer(player);
                Puts("Red Team");
                return;
            }
            
        }

Error:

(14:14:29) | [Koth] RelationshipManager+PlayerTeam
(14:14:29) | Failed to call hook 'PickTeam' on plugin 'KOTH v0.1.0' (ArgumentException: An item with the same key has already been added. Key: 0)
  at System.Collections.Generic.Dictionary`2[TKey,TValue].TryInsert (TKey key, TValue value, System.Collections.Generic.InsertionBehavior behavior) [0x000c1] in <eae584ce26bc40229c1b1aa476bfa589>:0 
  at System.Collections.Generic.Dictionary`2[TKey,TValue].Add (TKey key, TValue value) [0x00000] in <eae584ce26bc40229c1b1aa476bfa589>:0 
  at RelationshipManager+PlayerTeam.AddPlayer (BasePlayer player) [0x00052] in <32dc9dfab36748728a319b6b3ccd8f41>:0 
  at Oxide.Plugins.KOTH.PickTeam () [0x00078] in <00c7a55eb7a94d7db05801997e174e8b>:0 
  at Oxide.Plugins.KOTH.DirectCallHook (System.String name, System.Object& ret, System.Object[] args) [0x000d2] in <00c7a55eb7a94d7db05801997e174e8b>:0 
  at Oxide.Plugins.CSharpPlugin.InvokeMethod (Oxide.Core.Plugins.HookMethod method, System.Object[] args) [0x00079] in <60c318df79ed41688ea59335e48d61ad>:0 
  at Oxide.Core.Plugins.CSPlugin.OnCallHook (System.String name, System.Object[] args) [0x000d8] in <9882f28dc2204b4dba514a9ad18f5042>:0 
  at Oxide.Core.Plugins.Plugin.CallHook (System.String hook, System.Object[] args) [0x00060] in <9882f28dc2204b4dba514a9ad18f5042>:0