In 2013, I visited Arches National Park twice; once in March and once in July. I took lots of photos during both of those trips.
During the March trip, the sky was a bit overcast and rather a dull, grey color. Here is an example of the original photo with the dull, grey sky and the same photo with the replacement sky
Here are some shots of Delicate Arch. The original photos and then the faux watercolors I made with Aguarelleum in Photoshop. The skies in these photos are the actual skies, and not replacement skies.
The following photos all had dull grey skies, so I replaced the skies with skies that are a bit more interesting. And yes, several of these photos have the exact same sky as others. I used the Sky replacement process in ON1 Photo Raw to replace the skies.