I have lost Coleus in the house when our power was out for 8 days after an ice storm. I had them in an unheated room under lights, and discovered that the lights were keeping it warm enough for them. Coleus are damaged by temperatures in the low 40'sF (around 4.5 degrees Celsius).
I have also had problems keeping mature Coleus plants alive and happy when they have been growing outside and I bring them inside in fall. They usually dislike the change of environment, however, cuttings rooted late in the season perform well inside under lights. It may require a greenhouse to keep one growing and get it really large.
