How to change color on click?

local cd = script.Parent

cd.MouseClick:Connect(function()
      script.Parent.Parent.BrickColor = BrickColor.new("Red")
end

You were pretty close. 2 things: First of all, there is no Red BrickColor. There is stuff like Maroon and Really red. Second of all, you forgot to place a close bracket at the end to close off the connected function.

local cd = script.Parent

cd.MouseClick:Connect(function()
      script.Parent.Parent.BrickColor = BrickColor.new("Really red")
end)