You need to have Revolution Mod 16 V1.3 installled in your fifa 16.
When adding kits for referees, a set consists of teamid values of 6004, 6005, 6006, 6007, 6008 and 6009. The kittype of referee kits is always 5.
You can also add referee kits for use in a specific match, for these only teamid 6004 is used. This is the precedence list for referee kits.
1. specifickit_6004_5_$_hometeamid_awayteamid.rx3
2. kit_#_5_$.rx3
3. kit_6004_5_$.rx3
4. kit_#_5_classickitdecade.rx3
5. kit_6004_5_classickitdecade.rx3
6. specifickit_6004_5_%_hometeamid_awayteamid.rx3
7. kit_#_5_%.rx3
8. kit_6004_5_%.rx3
9. kit_#_5_0.rx3
Ex: to create a referee kit (5) to brazilian league (7), you need to create a rx3 kit named: "kit_6004_5_7.rx3" or "kit_6005_5_7.rx3" or "kit_6006_5_7.rx3", etc (from 6004 to 6009, you can use a diferent referee kit color to each number) and then copy then to C
Program Files (x86)\Origin Games\FIFA 16\data\sceneassets\kit.
Then regenerate.
There is a notepad file named "general" located in \Origin Games\FIFA 16\data\fifarna\lua\assignments
You can chose kit collar adding:
assignTournamentRefereeKitCollar(7,0)
7=league, 0 = collar type