Dear Edward,

A variety of environmental stresses can cause browning of needles.  Such stresses include drought stress (which could have been over several years), injuries to the trunk, winter injury, damage from misapplied chemicals, or root problems. A thorough review of the tree’s location and recent history can help to diagnose these problems. Here is information on possible causes of browning needles.
https://planttalk.colostate.edu/topics/weeds-cultural-problems/2123-needle-browning-evergreens/

https://lancaster.unl.edu/many-causes-brown-needles-branches-pines/

It could be that your tree experienced cold weather damage to its newer needles at the top and at the extremities.  Winter cold injury can occur following fluctuations in temperatures during dormancy or during spring frosts and freezes following bud break. Signs of winter injury include:
Needles turn brown in late winter-early spring
Needles turn brown from the tip down, needle base often remains green
Needles at the tip of the branch are more severely discolored than those close to the trunk
Damage often only on one side of the tree 

Here is some additional information on cold injury. 
https://extension.umn.edu/planting-and-growing-guides/protecting-trees-and-shrubs-winter#brown-or-bleached-out-evergreen-foliage-1264310
 
https://www.canr.msu.edu/news/assessing_cold_injury_in_conifers

https://www.montana.edu/extension/broadwater/blog-article.html?id=18729

Winter watering is needed for trees in Colorado. Consider the year-round watering schedule for it and whether that could have contributed.  Dessication can combine with cold to cause browning.  There are techniques to lower the risk and susceptibility of winter damage. Your goal every fall should be to help your trees and shrubs prepare for the long winter. Do not fertilize or prune during the late summer or fall as this can stimulate growth. If it is a long dry fall and drought like conditions, there is often some root damage from lack of moisture. This can weaken or kill part of the plant and make it more susceptible to winter damage. Water in the fall as needed, but don’t overwater or water before a cold spell. Continue to water throughout the winter if the ground isn’t frozen and there is no snow cover. Remember that the needles remain alive and will transpire, so keeping the soil moist helps reduce winter damage.

Because it is somewhat difficult to diagnose the browning of needles, and if you value the tree, it may be worth consulting a certified arborist for a diagnosis.  

Thank you for your inquiry and best wishes for your tree.