People often view Colorado as being a dry, dusty environment that doesn't support many popular shade trees. However, much of Colorado, including most of eastern Colorado, is in USDA Climate Zone 5. As such, many good shade trees will grow in eastern Colorado. The only thing to keep in mind is that some trees may need supplemental water during drier seasons or droughts.
The red maple, or Acer rubrum, is very well-suited for soils and growing conditions in eastern Colorado. This tree is native to North America. Its shallow root system can have a tendency to dry out, so be sure to water this tree during dry periods. This tree grows quite large. It can reach heights of 120 feet and can reach spreads of 50 feet wide. The red maple is very tolerant of different soils and should grow in most eastern Colorado soils. This tree usually turns red in the fall, but in some years it may turn yellow.
The Katsura tree, or Cercidiphyllum japonicum, is a disease-resistant tree that grows well in Zone 5. This tree can reach 100 feet tall and between 50 and 70 feet in diameter. The Katsura features a fan-shaped crown at full growth that can resemble an elm. The leaves of this tree are heart-shaped and turn gold in the fall. This particular tree needs full sun to thrive and will not grow well in shade. In eastern Colorado, the main problem you may find with this tree is its water requirement. It requires a lot of water. However, with adequate irrigation, it can make a good shade tree in many parts of eastern Colorado.
The Turkish Filbert, or Corylus colurna, is an ideal shade tree for many parts of eastern Colorado. This tree can reach 80 feet tall and can have a spread as wide as 35 feet. It is drought tolerant and will grow in almost all soils. This tree is disease resistant and can deal well with cold temperatures and does well during both windstorms and snow storms. Even though it is drought tolerant, it requires supplementary water the first few years after planting and doesn't do well if transplanted.