Adding a new color involves changing the animation so the luggage carts arrive with that new color luggage on board. For you to think it is a requirement is pretty selfish of you, Umberto wasn't required to create and release GSX, it was his choice. What he adds to it should also be his choice.
This is not a freeware product.
This customer paid for the product and has the right to ask the question regardless.
The creator of the product must answer the question regardless.
Now of course the creator of the product may or may not now or later offer a variant if they choose to do so @ no obligation and the buyer should understand that.
Now to get back to your comment.
You comment is cheeky, I do not know if you are part of the development team & if you are, future buyers who wish to purchase this product should be cautious because a good buy does not stop at the purchase and receiving of a product, but also in the FRIENDLY & efficient service that comes with said product.
Your customer care if you are part of the development team then leaves a lot to be desired.
If you are just a regular poster then the developers should do the right thing and censor your post.