@richsteer: Go to => Appearance => Customize => Additional CSS and add the following CSS Code.
To change the color of the active page and menu item on hover
.main-navigation .current-menu-item > a, .main-navigation .current-menu-ancestor > a {
color:#ffa100;
}
.main-navigation li:hover > a, .main-navigation li.focus > a {
color:#ffa100;
}
To make header transparent and show background only when scrolling down
.site-header {
background:none !important;
}
.site-header.is-sticky {
background:#131787 !important;
}
To change color of other menu options which are currently white
.main-navigation a {
color:#000;
}
To change the color of to top button
.backtotop:hover, .backtotop:focus {
background-color:#131787;
border-color:#131787;
}
.backtotop {
border:2px solid #131787;
color:#131787;
}
To change color of the text-widget at the bottom
#text-3, #text-3 a {
color:#131787;
}
It is not possible to change the color of LinkedIn and Twitter logo as it seems you have used a .png image for that purpose.
You can check out the additional-features available in the pro version of the theme and make your decision to upgrade.
Let me know if the CSS code work out.
Regards,
Skandha