website_mail_snippet_responsive/views/res_config_view.xml

<?xml version="1.0" encoding="utf-8"?>
<openerp>
<data>

    <record id="view_website_config_settings" model="ir.ui.view">
        <field name="name">Email Application</field>
        <field name="model">website.config.settings</field>
        <field name="inherit_id" ref="website.view_website_config_settings"/>
        <field name="arch" type="xml">
            <xpath expr="//group[@string='Menu']" position="after">
                <group string="Mail">
                    <label for="id" string="Mail button color"/>
                    <div>
                        <div>
                            <field name="mail_button_color" class="oe_inline"/>
                        </div>
                    </div>
                </group>
            </xpath>
        </field>
    </record>

</data>
</openerp>