OE视图开发

[gandell]

<record id="view_order_tree" model="ir.ui.view">
            <field name="name">sale.order.tree</field>
            <field name="model">sale.order</field>
            <field name="type">tree</field>
            <field name="priority">2</field>
            <field name="arch" type="xml">
                <tree string="Sales Orders" colors="grey:state=='cancel';lime:otherstate=='intercept';blue:state in ('waiting_date','manual');red:state in ('invoice_except','shipping_except')">
                    <field name="name"/>
                    <field name="date_order"/>
                </tree>
            </field>
        </record>

这个是订单的Tree视图  我想修改那个tree的colors的值  但是按照修改字段的那种写法不行  求指教