Unable To Cast String to Token [ HP bar script ]?

local char = script.Parent
local gui = script.HealthBar
local humanoid = char.Humanoid

gui.Parent = char.Head

humanoid:GetPropertyChangedSignal("Health"):Connect(function()

    local healthChange = humanoid.Health/humanoid.MaxHealth

    local healthColor = Color3.fromRGB(255,0,0):Lerp(Color3.fromRGB(60,255,0), healthChange)

    gui.Health.Meter:TweenSize(UDim2.new(healthChange,0,1,0),"in","Linear",1)

     gui.Health.Meter.BackgroundColor3 = healthColor


end)

Is it the Tween? I cant tell