Cook potatoes in salted water until fork tender; let cool and cut into 1-inch chunks. Place potatoes and the vegetables in a shallow dish or container. Pour marinade over vegetables. Cover and refrigerate for 2 hours.
Preheat an outdoor grill to medium heat.
Remove vegetables from the marinade, reserving marinade
. Thread vegetables onto skewers, alternating colors. Cook skewers on grill
until vegetables are lightly charred all over, about 10 minutes, basting with reserved marinade and turning occasionally.