Solution for this topic

It is displaying fine when you visit portfolio page http://www.cebabbage.co.uk/portfolio/ as shown in the attached screenshot.

If you want it to display highlighted also when you visit individual portfolio page then you can achieve it by adding the following CSS code in the Custom CSS code option of your theme on the below path.

Admin Area -> Appearance -> Theme Settings -> Custom Code -> CSS Code

body.single-fw-portfolio #header-navigation .sh-nav li.menu-item-7967 a {
    color: #ec1968 !important;
}