local TweenService = game:GetService("TweenService")

-- create part 1
local part = Instance.new("Part")
part.Size = Vector3.new(10, 10, 1)
part.Position = Vector3.new(0, 5, 0)
part.Anchored = true
part.Transparency = 1

-- create decal
local decal = Instance.new("Decal", part)
decal.Face = Enum.NormalId.Front
decal.Texture = "http://www.roblox.com/asset/?id=1145367640" -- white circle

-- add to workspace
part.Parent = workspace

-- create tweens
local redTween = TweenService:Create(decal, 
	TweenInfo.new(1, Enum.EasingStyle.Linear, Enum.EasingDirection.Out),
	{Color3 = Color3.new(1, 0, 0)}
)
local greenTween = TweenService:Create(decal, 
	TweenInfo.new(1, Enum.EasingStyle.Linear, Enum.EasingDirection.Out),
	{Color3 = Color3.new(0, 1, 0)}
)
local blueTween = TweenService:Create(decal, 
	TweenInfo.new(1, Enum.EasingStyle.Linear, Enum.EasingDirection.Out),
	{Color3 = Color3.new(0, 0, 1)}
)

-- play tweens
while true do
	redTween:Play()
	redTween.Completed:Wait()
	greenTween:Play()
	greenTween.Completed:Wait()
	blueTween:Play()
	blueTween.Completed:Wait()
end