[Phanx]

#1 - Change "t[f] = v" to "t[self] = v"

#2 - That means one of the bars you're modifying doesn't actually have 12 buttons. The whole section seems like it's probably not the best way to go about things, but I don't really feel like digging through the Blizzard actionbar code to rewrite it for you, so just do this to avoid the error:

	hooksecurefunc("PetActionBar_Update",  function()
		for i = 1, #petButtons do
			for j = 1, 12 do
				local name = petButtons[i] .. j
				local button = _G[name]
				if button then
					button:SetNormalTexture("Interface\\BUTTONS\\UI-Quickslot2")
				
					-- all the stuff here is fine, just indent it by one more level

					ColorButton(normalTexture)
				else
					print(name, "doesn't exist") -- you can remove this later
				end
			end
		end
	end)