Do rare-color weapons have special features in Dying Light?
Solution 1:
Item rarity will only affect the stats of your weapons. This means handling, durabilty and damage will be increased compared to a weapon of lower quality.
Keep in mind that every weapon also has a hidden level. This is why an orange quality item from earlier in the game will almost always be worse than a blue item from near the end of the game.
The only way to get special effects on your weapons (fire/bleed/toxic for example) is by crafting weapon upgrades.