This card shows an Autumn scene in the Rockies, where the foreground trees are deciduous and changing colors, while the background ones are evergreens. There are commonly differing tree combinations on the slopes of mountains, since various tree species are adapted to different altitudes and climates.
C. T. ART-COLORTONE, Sanborn Souvenir Co., Denver, Colo.
The description states simply:
1220 WHEN AUTUMN PAINTS THE TREES AND HILLS IN MAGIC COLORS
–It is also probable that the person coloring this image decided not to add more colors to the background trees. This card likely dates to the 1940s.