Hello,
Input color for the search we’ll fix in next theme update.
To change the color of the background you need to change the color of the container http://prntscr.com/gpj5w0 if you are using wide version, in other case it will use default color from dark.css or style.css. Side bg is visible when you choose boxed version, wide version has 100% of container that overlaps the site bg.
Regards