mdsk-sa
There is a background for the slide item, you can override with this custom CSS to remove it:
.acm-slideshow .owl-carousel .item:before {background: none !important;}
About the header, it simply due to the text color of menu item only, you can change to the color as you wish:
.navbar-default .navbar-nav > li > span, .navbar-default .navbar-nav > li > a {color: #777777 !important;}
paste these css code into the file: /templates/ja_techzone/css/custom.css (create this file if it doesn't exist now)