- Version 1.5.5.x - 1.5.6.x

1. Find and edit file "fnt_fancy_product_designer.xml"

2. Change button "Customize" style with class you need

- Version 2.0.x

 Admin control

1. Delete Fancy product design at Extensions/Modifications

2. Find and change file name "install.xml"

3. Change button "Customize" style with class you need

4. Install new file "install.ocmod.xml" at Extensions/Modifications ( don't forget Refresh after install)

With version 2.0.x, we can buy an extension can help us edit ocmod file directly ( don't need uninstall or reintall, it means doesn't need step 1, 2, 4, just step 3 is ok)

I got an extension here http://codecanyon.net/item/ocmod-editor-opencart-20-modification-editor/9808367 or we can use another extension what it can.