To prevent the randomization of traffic light colors, why not use the "is_random" color attribute with a black color ?
I think you're suggesting to use the is_random condition to randomize everything except the light color? That would definitely work 👍
The reason I left out randomization entirely is because I deemed it not worth it. In context, I don't think anyone will notice traffic lights that have a slightly randomized metallic color. So it's easier to exclude all together imo. Reserve randomization for things that are more clearly noticeable.