I wouldn't have thought the creamy leather (doesn't look like frost, but might be) was very common on a Sunset 350, at least it isn't in other countries. Usually the frost leather came on silver and white cars, with some exceptions.
Ultimately it's you that has to drive the car for however long, months, years etc and live with the car/colour, so you should be happy with your choice, or you will end up selling the car. Whether it's the GM or the Sunset.
GM = good as it doesn't show the dirt as much as other colours & a bit more conspicuous.
Sunset = almost glows in the sunshine, when you have some : P & it's easy to find in a line or carpark.