Our authorized USA Kit Dealer is PedalPartsandKits (see home page) which do take the additional measures to make sure that everything is done our way. Mammoth simply purchases boards at wholesale from me and makes kits. I get no commission etc.
That said I can see why they do not perhaps go out of their way to offer a Bi-Color LED in their kit. That is a guess of course as I do not really have much of a relationship with them. You can however use a standard on/off LED by not using the white pad which is to represent the “Off” color.
If you decide to purchase future kits I can highly recommend PedalPartsandKits since they not only provide everything needed per our build specs (including sockets) but also each and every enclosure can be ordered hand-drilled to be be a perfect fit to each of our boards. They cost a bit more but there is a lot more time and effort put into making each kit a perfect fit.
I hope that helps.