odoo-module-web_widget_color/view/web_widget_color_view.xml

<?xml version="1.0" encoding="UTF-8"?>
<openerp>
    <data>
        <template id="assets_backend" name="web_widget_color assets" inherit_id="web.assets_backend">
            <xpath expr="." position="inside">
                <link rel="stylesheet" href="/web_widget_color/static/src/css/widget.css"/>
                <script type="text/javascript" src="/web_widget_color/static/lib/jscolor/jscolor.js"></script>
                <script type="text/javascript" src="/web_widget_color/static/src/js/widget.js"></script>
            </xpath>
        </template>
    </data>
</openerp>