Two apps that include Colorado wildflowers are available for Apple and Android phones. ( I do not benefit from the sale of either one.)
Colorado Rocky Mountain Wildflowers has more than 500 flowers and is very user friendly with multiple ways to search for flowers to make an ID. It is very comprehensive with maps and botanical information.
Another app is Rockies Alpine Flower Finder that currently has 156 flowers with more to come. It is also user friendly. It focuses on alpine and montane flowers throughout the Rockies, so encompasses more than just Colorado.
Rocky Mountain Wildflowers, an excellent and colorful site
Eastern Colorado Wildflowers, another good site for our state of Colorado
Guide to Colorado Wildflowers, Volume 1 & 2 by G. K. Guennel
Wildflowers of the Rocky Mountains by George W. Scotter and Halle Flygate.
Rocky Mountain Flora by James Ells
Colorado Rocky Mountain Wildflowers presented by Denver Plants
Southwest Colorado Wildflowers
Colorado State University Herbarium Wildflower Photos
Wild About Wildflowers by Katherine Darrow
Meet the Natives: A Field Guide to Rocky Mountain Wildflowers, Trees, and Shrubs
by Walter Pesman and Dan Johnson
Wildflowers of the United States
Reference List for Colorado Wildflower Identification
For more information on noxious weeds, consult the
Colorado Weed Management Association
web site at http://www.cwma.org/