Which setting allows me to remove that rectangle/border in the active page? I cannot find a setting in the theme.

I tried putting this into the additional css but it doesn't work.

.primary-menu a { border: #00ffff !important
;}

I have also tried including these codes but nothing seems to work

nav[role="navigation"] li.menu-item-current a, nav[role="navigation"] li.menu-item-active a {
    border: none;
}

For my particular case, this worked:

#site-header:not(.shrink) .header-colors-light.header-style-3:not(.header-layout-overlay) #primary-menu.no-responsive > li.menu-item-current > a, #site-header:not(.shrink) .header-colors-light.header-style-3:not(.header-layout-overlay) #primary-menu.no-responsive > li.menu-item-active > a, #site-header:not(.shrink) .header-colors-light.header-style-4:not(.header-layout-overlay) #primary-menu.no-responsive > li.menu-item-current > a, #site-header:not(.shrink) .header-colors-light.header-style-4:not(.header-layout-overlay) #primary-menu.no-responsive > li.menu-item-active > a {border: 0px solid #00ffff;}

No thanks, as you can see I figured something out. Let's keep the thread here so others can look up the problem. I used TheGem Cryptocoin template.