One of the most important factors to consider when choosing an exterior color is; Colorado gets 300 plus days of sun annually. This means the south sides of homes are just constantly getting beat with sun.
The Bad news:
On a very basic level, darker colors are more photosensitive than light colors, meaning they will attract more of the sun's harsh rays, causing the resin of the paint to break down. On a deeper level, when you take a look at what paint really is, it is primarily made up of two parts, the pigment, or the color, and the resin, or the hard protective part of the paint. Aside from a few exceptions, most all of the paint in the store is a can of resin that needs tint dye added to it to be transformed into the exact color you are after. So, one important reason dark colors fade faster is; they actually have less paint in the can to start off with. When you imagine a can of paint, you have a gallon bucket, the buckets they use for darker colors are categorized into bases. Without boring you to death, you have light bases and deep bases. The light bases are almost full leaving very little room for dye, the dark bases, on the other hand have a lot more room for dye, and the darker the color the more room they need. Then, in order to get that color to be really dark, what they're going to do is; put the can under the tinting machine and fill it a great deal with actual tint. The same tint they use weather you're buying interior or exterior paint. That's why you run into issues with fading, even the better paints struggle with that because of the ratio of tint to good quality paint built to defend against exterior elements.
The Good News:
If you're absolutely attached to having a dark color on your home, and you don't plan to paint again any time soon, you can do a full prime and use the best quality paint available. Doing a full prime will create a fresh new layer for the new paint to stick and the bond will slow the breakdown of the resin in the new paint. Also, if you have a color that is border line in terms of shade of darkness, something that we can do is; determine, if what base the color needs to be made in. So, there if there's a potential it can be made in a medium base that's good news and will definitely extend the life of your paint
Ultimately, if the goal is longevity and saving money in the long term, the obvious choice is to avoid darker colors, and stick to lighter shades. However, if getting the exact color you want is your biggest concern, well, I say do what you want YOLO!