The game is really great. But I like others I also was confused by the colors and tried to match via the parcel's band. Then I thought the different colors might is a feature coming soon and I just have to put the package always in the same slot.
That I've to check against the color of the package I first noticed when it started with two packages at once.
But as mentioned: besides that a really nice and creative game. May you also should think about making a mobile version :-)