I don't know how this happened but every time I zoom in and out all dead NPC's, Ammo and Weapons have this strange green glow.
This is the PC Steam Version

[media]http://www.youtube.com/watch?v=owSbjqUc1ic[/media]


My specs are
OS: Windows 7 Ultimate 64-Bit
Memory: 8GB Corsair DDR2 800Mhz
CPU: Intel Core 2 Duo E8400 3.0Ghz
GPU: ATi HD5770 1GB DDR5
HDD: Hitachi 320GB SATA-II
Monitor: 26" HDMI

That's what Rex's perk does.