Hi Mark:

Thuja pines are arborvitae, and even though they look like the perfect screen between houses, they are not so perfect in Colorado. They are susceptible to winter sun and wind damage and prefer a sheltered somewhat shady location. Once the leaves burn off and turn brown they do not regenerate and you can see the evidence of that everywhere. Here is an article I found in the CSU blog spot that might help you choose a substitute. 

Plant This Not That: Arborvitae Edition

Arborvitae (Thuja occidentalis) are evergreen trees which are prized by many homeowners for their deep green color, refined-soft texture and value as a year round screen plants. However, this year the weather we experienced along the Front Range (which has been discussed here and here) exposed one of their weaknesses. In our dry climate with its fluctuating and inconsistent temperatures in the spring they are borderline cold hardy.
While you can get away with planting Arborvitae in the right protected microclimate I thought I might highlight a few more reliable substitutes for them in the landscape.

Cooke Peak Arizona Cypress (Cupressus arizonica 'Cooke Peak')
This evergreen plant has a nice texture and attractive and aromatic spearmint green foliage color. This selection is drought tolerant and reliably cold hardy along the Front Range. The habits of individual plants can vary somewhat.

Pinion Pine (Pinus edulis)
Pinion Pine is a native evergreen which is smaller in stature and not as dense as Arborvitae. However, it is very drought tolerant once established and does add winter interest to a landscape. Pinions sited in more moist sites such as irrigated turf grass may struggle.

Rocky Mountain Junipers (Juniperus scopulorum various cultivars)
There are many clones of Rocky Mountain Juniper which are suitable for use as screen plants, very drought tolerant once established and reliably cold hardy. While they do lack the smoother more refined texture of arborvitae they offer a wider range of foliage colors. The cultivar ‘Woodward’ is upright selection with dull green foliage which has a strong central leader and is less prone to damage from snow loading than other upright cultivars. It may be difficult to find but it’s worth the search. Selections such a “Gray Gleam”, “Cologreen” and “Moonglow” all have more gray-green or blue-green foliage and are more commonly available at nurseries and garden centers. All three earned good ratings on the Front Range Tree Recommendation List.

Upright Oaks (Quercus various cultivars and crosses)
I know this seems like a stretch but hear me out. While they are not evergreen most of the upright oaks are dense enough to provide some screening even in the winter. Many of them also have attractive deep green foliage and some even get reddish fall color. Most are narrow enough to fit in smaller yards of many new homes. Crimson Spire Oak (Quercus alba x robur 'Crimschmidt')is one upright hybrid with very attractive fall color. Columnar English Oak (Quercus robur 'Fastigiata') and the other upright English Oak cultivars often exhibit juvenility, retaining dead leaves on their branches thoughout the winter. Some people find this unattractive and it can increase snow loading, however, it does add extra screening value in the winter.

Another plant to check out is this one: 

https://plantselect.org/plantstories/yearning-for-tuscany-try-woodward-juniper/

Plant Select selections are usually well suited for our location. And if you need one more suggestion: this is not an evergreen but you might consider it. It's the only native maple we have in Colorado and does well here despite our alkaline soil. It grows fairly fast and came through the last few sudden super cold nights without a problem, at least in my yard. It's called Bigtooth Maple, Acer grandidentatum, and is readily available in nurseries.

I hope these suggestions are helpful.