What I expected to happen was...:
Command:
/give @p minecraft:leather_helmet 1 0 {display:{color:255000000}}
or
/replaceitem entity @p slot.armor.head minecraft:leather_helmet 1 0 {display:{color:255000000}}

I expected to get some red Leatherhelmet with Hex-Code FF0000.

What actually happened was...:
I became some cyan Leatherhelmet with Hex-Code F32FDC0.
This happened with Chestplate, Leggings and Boots, too.
This happened with other colors, which use red, like yellow and orange and white, too.

Steps to Reproduce:
Command:
/give @p minecraft:leather_helmet 1 0 {display:{color:255000000}}
or
/replaceitem entity @p slot.armor.head minecraft:leather_helmet 1 0 {display:{color:255000000}}