The hexadecimal string representing the armor color doesn't have any preceding 0 characters. Although this is a valid hexadecimal string, it is not a valid RGB string since it does not have all 6 characters.

Example:
The following command gives a pair of blue (#0000FF) leather boots. However, the color is instead displayed as #FF.

/give @p minecraft:leather_boots 1 0 {display:{color:255}}