Sounds like cold damage. The off-color leaves and wilting can show up immediately, several hours later or even a day after the plants have been exposed to cold temperatures. Poinsettias, flowering plants, and tropical plants need extra protection when moved from one location to another during cold weather. Cover the plants with paper, cloth or plastic. Double wrap the plants in extremely cold weather. Consider warming the car first and never leave plants sitting in a cold car while you run errands. At this point continue to give the plant proper care and wait to see if it survives.