Gardening

Here is a source of flowers for your area. These are all perennials, so you plant once and water while establishing and you will have a better garden each year and you don't do anything except occasional weeding and watering.

http://www.bhg.com/gardening/gardening-by-region/mountain-west-and-high-plains/types-of-mountain-west-perennials/

This is my favorite of the high country seed and plant companies
https://www.highcountrygardens.com/

Here are some shrubs.
http://www.highcountrygardens.com/perennial-plants/shrubs

My thoughts are that you choose the colors that you would like to see. I don't recommend things like lilacs as they are not native cultivars. They are from Europe I believe and natives are much more able to withstand all the elements of your area.

I'm working on my one acre native garden in Arkansas. It's sometimes fun and sometimes trying. We have so much humidity and water that all the non native invasive are troublesome. Also, the bugs. You don't have the bugs, lucky you.

Planning the garden is almost as fun as looking at the finished product. Since you don't seem to have lots of time to devote I would definitely suggest bulbs and perennials. Plant them and you are done.

Good luck and enjoy the journey.