The easiest way to return your color is to place all of the mixed colors inside a plastic zip-lock bag and shipped in the smallest box possible. The glass color is not breakable, so no extra care is needed. Vandalia Glassworks uses two shipping addresses depending on the carrier.
USPS:
PO BOX 513, South Saint Paul, MN 55075
UPS or FedEx:
103 Concord Exchange N, South Saint Paul, MN 55075