Why won't my random color changer work?

I'm trying to make a button that changes the color of surface GUIs, but it doesn't do anything.

local button = script.Parent

 color = math.random(1,4)

button.MouseButton1Down:connect(function()
	if color == 1 then
		script.Parent.BackgroundColor3.new(40,40,40)
		script.Parent.Parent.Parent.Taskbar.BackgroundColor3.new(40,40,40)
		script.Parent.Parent.Parent.Taskbar2.BackgroundColor3.new(40,40,40)
		script.Parent.Parent.Parent.ImageLabel2.BackgroundColor3.new(40,40,40)
		script.Parent.Parent.Parent.StartMenu.BackgroundColor3.new(40,40,40)
		script.Parent.Parent.Parent.Settings.BackgroundColor3.new(40,40,40)
		
		
	if color == 2 then
		script.Parent.BackgroundColor3.new(255,0,0)
		script.Parent.Parent.Parent.Taskbar.BackgroundColor3.new(255,0,0)
		script.Parent.Parent.Parent.Taskbar2.BackgroundColor3.new(255,0,0)
		script.Parent.Parent.Parent.ImageLabel2.BackgroundColor3.new(255,0,0)
		script.Parent.Parent.Parent.StartMenu.BackgroundColor3.new(255,0,0)
		script.Parent.Parent.Parent.Settings.BackgroundColor3.new(255,0,0)
	
	if color == 3 then
		script.Parent.BackgroundColor3.new(0,255,0)
		script.Parent.Parent.Parent.Taskbar.BackgroundColor3.new(0,255,0)
		script.Parent.Parent.Parent.Taskbar2.BackgroundColor3.new(0,255,0)
		script.Parent.Parent.Parent.ImageLabel2.BackgroundColor3.new(0,255,0)
		script.Parent.Parent.Parent.StartMenu.BackgroundColor3.new(0,255,0)
		script.Parent.Parent.Parent.Settings.BackgroundColor3.new(0,255,0)
	
	if color == 4 then
		script.Parent.BackgroundColor3.new(0,0,255)
		script.Parent.Parent.Parent.Taskbar.BackgroundColor3.new(0,0,255)
		script.Parent.Parent.Parent.Taskbar2.BackgroundColor3.new(0,0,255)
		script.Parent.Parent.Parent.ImageLabel2.BackgroundColor3.new(0,0,255)
		script.Parent.Parent.Parent.StartMenu.BackgroundColor3.new(0,0,255)
		script.Parent.Parent.Parent.Settings.BackgroundColor3.new(0,0,255)
	end
end

Thanks if you can help, I'm also a bit of a noob at scripting.

One can set the Color3 of a Gui like so.

gui.BackgroundColor3 = Color3.fromRGB(0,0,255)

Make note, the code you have above would error. Please, have the output window open at all times.