<tree decoration-success="state=='confirm'" decoration-danger="state=='reject'">
<field name="product_id"/>
<field name="state" invisible="1"/>
</tree>
<!-- Here is the detail for available color -->
decoration-bf - shows the line in BOLD
decoration-it - shows the line in ITALICS
decoration-danger - shows the line in LIGHT RED
decoration-info - shows the line in LIGHT BLUE
decoration-muted - shows the line in LIGHT GRAY
decoration-primary - shows the line in LIGHT PURPLE
decoration-success - shows the line in LIGHT GREEN
decoration-warning - shows the line in LIGHT BROWN