I'm about 80% through the main quest, and just picked up a purple Desert Police Rifle. The attributes say it has 184 damage, 75 accuracy and 100 rate of fire. Somewhere along the way, I picked up a blue Advanced Police Rifle that has twice the damage at 368, with the other attributes being identical (other than price).
I also have Tahir's Weapon (a machete), that's orange and has 245 damage, and I've got some other blue machetes with more than three times that damage.
I'm wondering if the rare color (purple and orange) weapons have any special hidden features that make them worth keeping, as compared to the more available colors of weapons? The Borderlands games do that, so I was wondering if Dying Light has similar meanings to the rare weapons.