LightingController.cs
using Sandbox;

public sealed class LightingController : Component
{
	[Property]
    public RedLightGreenLight GameController { get; set; }

	[Property]
    public PointLight Light { get; set; }

	protected override void OnUpdate()
	{
		if ( GameController.State == RedLightGreenLight.GameState.Red)
		{
			Light.LightColor = Color.Red;
		}
		else
		{
			Light.LightColor = Color.Green;
		}
	}
}