Change hamburger or menu icon colour when in mobile view

when previewed in mobile layout, the menu hamburger (being white) disappears due to the white background unless i change the header/menu colour to black which then exposes the logos jpeg shape (white rectangle) and looks unappealing.

how do you change the colour of the hamburger icon when viewed in mobile view?

Link: SEPG

See here please: http://docs.athemes.com/article/61-mobile-menu-button-color

AWESOME thankyou!!