You can adjust the background color in ACP > Style properties > Header & Navigation : first row change the header adjust color.
To put border use CSS code in extra.less template.
As i said replace this value fade(@xf-paletteNeutral3, 15%) of the Header adjustment color row with the color code you want, like #FF6600 for orange and the background color of User/Inbox/Alerts/Search buttons will change.