Based on the provided content, there is no specific information regarding lighting recommendations for a master bathroom retreat.

The source material focuses on structural and functional spa features for the Denver area, specifically highlighting:

• Heated Floors: A highly popular feature in Colorado due to cold winters.
• Walk-In Steam Showers: Specialized wellness features that add humidity and warmth.
• Freestanding Soaking Tubs: Used as elegant, therapeutic focal points in the room.
• Curbless Showers: Popular for their modern look and accessibility benefits.

If you are looking for lighting advice, it is not covered in this guide, which emphasizes design-build aspects such as permitting, custom fabrication, and specific plumbing fixtures.