Ask Mr. Smarty Plants

Sure, it's possible, you can plant anything you can dig a big enough hole for. The questions are (1) how far out of your area will you have to go to find that tree to purchase and (2) will it live?

Picea pungens (blue spruce), also known as Colorado spruce or Colorado blue spruce is found growing naturally no nearer to Boerne than the mountains of New Mexico and western Colorado. In these areas, the tree is in its comfort range of average January temperatures of 12 to 16 deg. F, and maximum July temperatures of 70 to 72 deg. F. In Central Texas, 72 deg. F overnight is considered a cold snap, much less during the day. Picea pungens is considered hardy in USDA Hardiness Zones 2 to 7. Kendall County, in the Texas Hill Country is in Zone 8b.

So, in answer to our first question, can it be purchased, the answer is probably not. The preferred propagation method for this plant is by seed. The main reason for this is that transplanting conifers, which usually have taproots, is very difficult, as damaging the taproot can mean death to the tree. Shipment would be expensive and survival not be guaranteed. It seems very unlikely, under those conditions, that your neighborhood nursery is going to be carrying this tree for sale. In answer to the second question, you can draw your own conclusions. The Lady Bird Johnson Wildflower Center is dedicated to the care, protection and propagation of plants native not only to North America but to the area in which they grow naturally. You already know where the Colorado blue spruce will grow, and can make your own judgment on where it won't grow.

For more information, see this website from Ohio State University on Picea pungens.