Whilst wearing any combination of default game armor, textures will override each other.
Look at whats actually equipped compared to what I visually wear.

^Boots override both chestplate and helmet textures but if both a helmet and chestplate is worn with boots, the chestplate will override the helmet.

^As you can see here, boots override chestplate

^However a chestplate by itself is fine

^A helmet and chestplate will swap textures (Again only for vanilla armors)

^Boots will override the helmets texture but a helmet by itself is fine.

ANY combination involving pants leaves the pants unaffected and does not let the pants effect other armor

Testing was done strictly with MoBends, Optifine, IChunUtil, Back Tools, Wearable Backpacks, and Block Armor, no other mods were active or in my mod folder.