No distinction between main button and navbar when the two are close

[matei-radu]

When a main button is near the navigation bar (when for example the user is scrolling) it is not clear where the button ends and navigation bar begins. See screenshot:

This distinction must be clear just by looking at the items:

• The buttons could have a different color from the navigation bar
• The navigation bar could have a thin bottom border of a darker shade of blue.