We have many books on gardening in the West, some specific to Colorado. Check these out:
The Complete Guide to Western Plains Gardening: Techniques for Growing Landscape & Garden Plants in Montana, Colorado, Wyoming, Northern Kansas, Nebraska, North Dakota, South Dakota, Southern Manitoba, Southern Saskatchewan, Southern Alberta by Lynn Steiner.
Organic Gardener's Companion: Growing Vegetables in the West by Jane Shellenberger
The Low-Water Flower Gardener by Eric A. Johnson & Scott Millard
Xeriscape Colorado: The Complete Guide by Connie Lockhart Ellefson and David Winger
Find more at Gardening - Colorado