how do I make a script affect every part in a group?

im trying to change the color of every part in a group and I dont know how to do it, ive tryed to do an in pairs thing and it only changed one parts color in the group

this is what my script looks like

while true do 
	for i, v in pairs(game.Workspace:WaitForChild('stage1').stagetest:GetChildren()) do

		if v:IsA('Part') then 

			wait(math.random(1,5))

			v.BrickColor = BrickColor.new("Lime green")


			wait(math.random(1,5))
			v.BrickColor = BrickColor.new("Really red")


		end
	end
end

im trying to affect items in a group that is inside of another group so thats why its stage1.stagetest

you might have been doing it wrong, so try this:

for i,v in pairs(script.Parent:GetChildren()) do
      if v:IsA("Part") then
           v.BrickColor = BrickColor.new("Your color")
    end
end

put the script inside the model for it to work. Hope it works!