I just discovered this regression is due to Lighting LUT Quickfix #2367.
Exact commit will be 88f409aec9a490138012cde35789d1f21f20818f
Before (commit 14f8065843bf865cbd0f2f34eabf54c37e52df81) / After (commit 2f746e9946f78a2e283dfdcbeda9cf332e44d099) / Console
[Pokémon X/Y]

Source: Before | After | Console (Darker background unrelated)
[Gallery] New 3DS XL – Pokémon X
[Pokémon Alpha Saphire]

Source: Before | After | Console (Bubble effect unrelated)
//Gallery of images to be added later
[Pokémon Sun & Moon]

Source: Before | After | Console
[Gallery] New 3DS XL – Pokémon Sun
OS: _Windows 10 Pro Insider Preview build 15025 (codename Redstone 2)_
Processor: _Intel® Core™2 Duo CPU E7500 @ 2.93GHz, 2926 Mhz, 2 Core(s), 2 Logical Processor(s) [Overclocked to 3.7 GHz]_
GPU: _nVidia GT 610 2GB DDR3 (Asus)_
Driver: _Version 376.53_
OpenGL: _Version 4.5_
Can we get some reference screenshots from hardware please?
We should test this with MESA SW rendering etc. too. Maybe this is due to some texture filtering improvements in the host graphics driver?
We should also have a look at the LUTs used by Pokemon and how we treat them.
Reference screenshots made on hardware (New 3DS XL) for Pokemon Alpha Sapphire. I'll add reference shots for X/Y and Sun/Moon as pictured (if I'm able to, the timing on some of these screenshots is a little hard to catch, but we'll see) sometime when I get the time to.
Pokemon Alpha Sapphire

Video (Stream):
https://youtu.be/zgg3IDbvJdo
Pokemon X

Video (Stream):
https://youtu.be/AYF5NeH0Ask
Pokemon Sun
Coming Soon
_Lossless Video Files:_
https://mega.nz/#F!p7RjyYKA!xgoXkhafnNJvsDo_JFzIJw
I have added a gallery of images for Pokémon X and Sun for comparison. Most are pixel perfect accurate in Pokémon X (except for battle scene) but not in Pokemon Sun due to the character always in motion.
Are all these fixed in current master?
All fixed in #2792
Most helpful comment
Reference screenshots made on hardware (New 3DS XL) for Pokemon Alpha Sapphire. I'll add reference shots for X/Y and Sun/Moon as pictured (if I'm able to, the timing on some of these screenshots is a little hard to catch, but we'll see) sometime when I get the time to.
Pokemon Alpha Sapphire

Video (Stream):
https://youtu.be/zgg3IDbvJdo
Pokemon X

Video (Stream):
https://youtu.be/AYF5NeH0Ask
Pokemon Sun
Coming Soon
_Lossless Video Files:_
https://mega.nz/#F!p7RjyYKA!xgoXkhafnNJvsDo_JFzIJw