Stephanie.France on "[Plugin: Contact Form 7] CF7 specific style : disappear with version 3.5.1"

I'm using WP 3.6. And I've just uploaded CF7 3.5.1.

My specific background colour had disappear, and I'm unable to fix it again using (at contact-form-7/admin/css/styles.css)

.wpcf7
{
background-color: #EFEFEF;
}

nor :

div.wpcf7
{
background-color: #EFEFEF;
}

Could you please help me? Thanks a lot in adavance !

http://wordpress.org/plugins/contact-form-7/