Modify the simplewand.png texture to a different color.
Change your modid and domain to something else
To achieve this...
Modify both the modid entry in modinfo.json, and change the name of the 'simpleitem' folder in 'assets'.
Rename your 'Simple Wand'
To achieve this...
Change the entry for simplewand in your en.json lang file.
Create another wand with a different color
To achieve this...
Create a copy of the texture with a different name and color, and a duplicate itemtype file. In the new itemtype file, change the item code and change the texture property to your new texture path. Don't forget to add new lang translation entries!
