The issue is that on iOS devices textures are displaying significantly darker than expected.
I did a color calibration with my monitor to get a more accurate representation of the texture. I set the texture the texture group UI, and those did not change the issue. A workaround is available by unchecking the sRGB box in the texture settings, as well as changing the compression settings to UserInterface2D. This makes the texture much brighter and shows up less dark on the iOS device.
Worked in (4.14.3) CL 3249277
Broken in (4.15.P2) CL 3269047
Only affects iOS?
Yes, Issue was tested on Android and does not occur in 4.15.P2 or 4.14.3
Result: Texture on iOS Device is much Darker (or Redder in this specific case) than what is on your Editor Screen
Expected: The colors of the texture should match (as close as possible)
Head over to the existing Questions & Answers thread and let us know what's up.