How to make sure no BrickColor is repeated when changing a group of brick's BrickColor randomly?

door = script.Parent  
local list = game.ServerStorage.Colors:GetChildren()
local list2 = game.Workspace.Colors4.pads:GetChildren()
local pm = game.ServerStorage.pm.Value
function onChatted(msg, recipient, speaker) 
	local num = 0
	--------------------------
	function colorCheck(tab,val) -- function, so you can do multiple times
		for _,v in pairs (tab) do
			if v == val.Value then
				return false
			else
				return true
			end
		end
	end
	------------------------------
	local source = string.lower(speaker.Name) 
	msg = string.lower(msg) 
	-----------------------------------
	local colors = {} -- table for brickcolors
	-----------------------------------
	if (msg == ":randomize") then 
	
	repeat 
	---------------------------------
	function change() -- so you can do multiple times
		local c = list[math.random(#list)]
		if colorCheck(colors,c) == true then
			list2[math.random(#list2)].BrickColor = c.Value
		else
			change()
		end
	end
	change()
	--------------------------------
	num = num + 1
	print(num)
	wait()
	until num == 9
	end
	num = 0
end 

function onPlayerEntered(newPlayer) 
newPlayer.Chatted:connect(function(msg, recipient) onChatted(msg, recipient, newPlayer) end) 
end 

game.Players.ChildAdded:connect(onPlayerEntered)