How do I make this script affect everything with the same name?

Personally I would use a For Loop to loop through and find all the objects you want with whatever specific functions you want. I would put these "Clones" in a model to make it easier and more clean. In my example I would do that.

Code:

while true do   --Wouldn't recommend using a while loop unless you absolutely need to, but I don't know anything more to help you prevent using this
    wait()
    if game.Workspace.TrelloSound.PlaybackLoudness > 350  then
    	for i,v in pairs(game.Workspace.Clones:GetChildren()) do --The model is named "Clones"
			if v.Name == "Flicker" then
				v.BrickColor = BrickColor.new("White") 
			end
		end
	elseif game.Workspace.TrelloSound.PlaybackLoudness < 350 then --Added in another check, didn't realize I didn't do that
		for i,v in pairs(game.Workspace.Clones:GetChildren()) do
			if v.Name == "Flicker" then
				v.BrickColor = BrickColor.new("Gold")
			end
		end
	end
end

If you have any problems or questions don't be afraid to comment and I would be glad to help. If this helped you don't forget to accept my answer. Also note that if you want to keep the parts in Workspace then just change it to your wantings.