A bouquet of coleus cuttings would be attractive in a pretty vase. In a warm house only.

Not a stupid question, actually. Coleus will prefer to root under warmer conditions than outdoors in Oregon, although if this were done later in the season, once the weather had reliably warmed up to stay above 55F or 60F at night, then Coleus will readily root outdoors in bright shade protected from wind. This time of year, definitely you would get better/faster results if done indoors or in a warm greenhouse.

Most plants will tend to root more quickly under warming/warm temps than under cooler winter conditions or height of summer when heat and dryer air make keeping the humidity levels favorable is more difficult. So late spring and early fall tend to be ideal outdoor temperature ranges for optimum rooting with least moisture/heat stress.

Thanks to both of you! I wasn't going to try it until later in the season anyway - it was more of a general "is this possible" kind of question. Maybe I'll try it when it gets warmer just for the fun of doing the experiment.

Coleus roots easily but I've never tried it outdoors.

Coleus roots ridiculously easily - which is why I have so much of it that I'm willing to do some experimenting. ;0)