I have some good idea for this project: do you know the tags colors in leather_chestplate for example color:16711680 , you can make this, if i define in a file config the id with a leather_chestplate for example and the color he can give that armor with that specified color?

This has been added as of ItemJoin v3.1 and will be uploaded soon! Thanks for your patience!

Version 3.1 has been released! Enjoy!
http://dev.bukkit.org/bukkit-plugins/itemjoin/files/26-item-join-v3-1/