Hi!
On the Theme Options -> Settings icon & Drop-down panel, with the Settings drop-down background gradient option: http://i.imgur.com/6VOqg6x.png
If you use the block layout for the drop-down, then the color is inherited from the theme, and can only be changed via custom CSS, like so:
[html].wpdreams_asp_sc.searchsettings {
background: #000000 !important;
}[/html]