Can Xbox One play xvYCC enabled Blu Rays ('Expanded Color')?

Unless the Xbox One clips black and white levels or converts YCbCr internally to RGB for output, the xvYCC content should be intact. You might need to force the projector to treat the signal as xvYCC though.

The Blu-rays that say Mastered in 4K will have a better overall picture than those that aren't. I don't see that they cost anymore, at least from Amazon. Sony previously did this with a line of pristine masters of DVD's some years ago. Here is the marketing
speak:

The Blu-ray “Mastered in 4K” collection will set a new standard for Blu-ray HD picture and sound, creating the ultimate 1080p home entertainment experience. Created from the highest quality 4K source materials with new expanded color*, consumers can enjoy
a brilliant picture with exquisite detail using their existing Blu-ray player or PlayStation®3. The Blu-ray “Mastered in 4K” collection is optimized so that 4K Ultra HD TV owners can take full advantage of the new 4K upscaling technology, delivering an outstanding
near-4K experience. “Mastered in 4K” Blu-rays also work with all 1080p HDTVs for spectacular high definition picture and sound.

*Expanded color requires xvYCC-compatible TV and Blu-ray player

Why “Mastered in 4K” Blu-ray?

• Get the best Blu-ray picture possible, mastered from 4K source materials

• Push your TV to the limit with a high bitrate digital transfer for an immersive visual experience

• Ideal solution for new 4K TV owners and great for Blu-ray collectors

Notice the "near 4K" phrase? In any case they should look better when played back on equipment that will utilize the high bitrate of the disc.

YCC was not enabled but, but color was, No updates for blu ray app. I am thinking it is the blu ray app as netflix on xbox outputs Dolby Vision without issue

I can verify this issue...Netflix UHD does not work on Xbox One S. I have a Vizio M55-D0 with the latest firmware enabling HD10 support. My TV is now recognized by the One S video settings as 4K HDR capable. I am able to enable HDR support and it works beautifully
with the Blu-Ray app (Mad Max 4K Blu Ray playing 4K, 24fps, HDR as verified by the Vizio settings app). However when I start Netflix, the screen flashes, colors mute, and video fails to switch to HDR or 24fps. Netflix app is clearly broken right now for HDR.
If I switch HDR off on the One S, Netflix app is fine, plays 4K correctly, colors are fine obviously no HDR.

Same here with a Samsung KS7000, connected with the XBOX ONE S original HDMI cable and with all the correct settings enabled (HDMI UHD Color, XBOX settings, etc.). All the HDR content like 4K HDR blu-rays or games like NBA 2K17 look like the colors are
washed out. Everything seems dimmed, like having a white filter.

I bought XBOX ONE S to be used as a game console but also as a blu-ray player to complement my 4K HDR TV. Please Microsoft address this issue and solve it ASAP.

Thanks!!