Colorado is a great place to really study Dark-eyed Juncos. At the yard feeders you can see many of the sub-species. Lately, I have seen mostly Slate-colored but there's always an interesting one or two, like the Pink-sided seen on the feeder above.
When's the last time you really looked at a Junco and gave it a second glance? I suggest you spend a little time on our common yard feeder bird and really admire the differences you can see in careful observation.