Colorado has a number of different climate zones. By grafting hardy apple varieties to a root stock hardy for your particular area of Colorado, you can grow apples in many parts of the state. When selecting a grafted variety, look for one that is cold hardy down to at least the zone in which you live. However, hardier fruit may do better.
Areas in Colorado where apples grow well can easily support a 5-in-1 or 3-in-1 tree. On these trees, multiple varieties of apples are grafted onto a hardy root stock that can survive the winter. The varieties included on each tree vary. By selecting trees with species resistant to fire blight and that ripen in early October in zone 5, you can get multiple types of apples from a single tree.
Honeygold apple trees grafted on to sturdy root stocks can grow and produce very well in Colorado. Honeygold trees grow to between 10 and 30 feet, depending on the root stock. They are between 10 and 15 feet in spread. Like other apple trees, they need full sun. Honeygold apples do well in climate zones 3 to 9. The fruit from the honeygold tree ranges from golden to a yellowish green. They sometimes have a redish cast. They are good for pies, sauces, eating, canning and freezing.
Sweet sixteen apples are a red apple that are very crisp and juicy. They have a yellowish flesh and a flavor reminiscent of sugar cane and spicy cherry. These apples ripen in mid-season and can be stored for 5 to 8 weeks, depending on when you harvest them. When grafted to an appropriate Colorado hardy root stock, these apples can thrive. Like other apples, they need full sun and adequate water--preferably both frequent and deep, depending on your soil.