blue dot on collapsed navigation (behind hamburger icon) – how to delete it?

When checking the site on iPhone and iPad there appears a blue round field behind the hamburger icon. I cannot see this when editing on the computer, upfront, mobile views. How to change that color to the navigation color (to that it is not visible) or how to delete it?
This is the site:

And the logo moves, depending on viewport, vertically. How to control that? (see screenshots below)