To reproduce:
1. Open project
2. Open '2Images' scene
3. Open game view

Expected: edges of both textures will be white
Actual: some edges becomes purple. If using editor in full screen mode, purple lines disappears(video attached)

Reproduced: 5.5.5p1, 5.6.4p4, 2017.1.2p4, 2017.2.1p1, 2017.3.0f2, 2018.1.0a7

Note: there is different repro results on different machines:

•Purple stripes on: iMac (21.5-inch, Late 2015), 2,8 GHz Intel Core i5, 8 GB 1867 MHz DDR3, ntel Iris Pro Graphics 6200 1536 MB, OSX 10.13.2
•Purple PVRTC texture corners only: iMac(Retina 5K 27-inch, Late 2015), Intel Core i7 4 GHz 32 GB, AMD Radeon R9 M395X 4096 MB, Mac OS X 10.12.4 (customer's machine)
•No repro on: iMac (27-inch, Late 2009), 3,06 GHz Intel Core 2 Duo, 4 GB 1067 MHz DDR3, ATI Radeon HD 4670 256 MB, OSX 10.11.6