I was halfway in making a minigame, and I tested the new /replaceitem command and typed this (/replaceitem entity @p slot.armor.chest leather_chestplate 1 0 {display:}) to immediately place a green leather tunic onto the player, but when I press a button linked to the command block, the armor was dyed black! I tried other things instead of the 3491355, such as green and 13 (wool ID for green), and it still doesn't work! The bug also appears with the /give command (/give @p leather_chestplate 1 0 {display:}).
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I would also strongly suggest updating your Java to the latest 1.7.60 http://www.java.com/en/download/.
When using a 32-bit browser on a 64-bit operating system the automatic version detection will only show the 32-bit version of Java, the 64-bit version needs to be downloaded manually: http://www.java.com/en/download/manual.jsp.
Cannot reproduce on default, which means the resource pack that you're using is broken.