Those grey/white areas are part of BuddyPress’ styling.
Use a tool like Firebug to inspect elements and figure out the tags/classes/ids you need to override with CSS.
#buddypress table.forum tr.alt td, #buddypress table.messages-notices tr.alt td, #buddypress table.notifications tr.alt td, #buddypress table.notifications-settings tr.alt td, #buddypress table.profile-fields tr.alt td, #buddypress table.profile-settings tr.alt td, #buddypress table.wp-profile-fields tr.alt td {
background: none repeat scroll 0 0 #222;
}