You probably missed some instances of the pink colour in the styles that target the menu on smaller screen sizes.
You’ll need to find all instances of pink in the original stylesheet and override them in your child theme or stylesheet.
This colour scheme replaces all the original pink with turquoise – you can replace it with your own blue if you’d like:
.nav-menu > li > a:after {
color: rgba(0, 0, 0, 0.3);
}
.main-navigation a, .social-links ul a:before { color: #494949;}
.menu-toggle, .menu-toggle:hover, .menu-toggle:focus { color: #494949;}
.main-navigation.toggled ul ul, .main-navigation.toggled ul ul a { color: #494949;}
.site-info a { color: #FFFFFF;}
.main-navigation a:hover, .main-navigation ul > :hover > a, .main-navigation ul > .focus > a { color: #494949;}
.main-navigation li.current_page_item > a, .main-navigation li.current-menu-item > a { color: #494949;}
.main-navigation li.current_page_item > a .sub-menu li a, .main-navigation li.current-menu-item > a .sub-menu li a, .main-navigation ul ul li.current_page_item > a, .main-navigation ul ul li.current-menu-item > a { color: #4F4F4F;}
body { background-color: #f0f0f0;}
.main-navigation, button { background-color: #74ccd1;}
a, .entry-title a:hover, .comment-meta a, .jetpack-testimonial .entry-title { color: #2B797C;}
.widget_flickr #flickr_badge_uber_wrapper td a:last-child, .widget-area .milestone-countdown .difference { color: #2B797C;}
.main-navigation ul ul a:hover, .main-navigation ul ul > li.focus > a { color: #2B797C;}
input[type="button"], input[type="reset"], input[type="submit"], #infinite-handle span { background-color: #2B797C;}
input[type="text"]:focus,
input[type="email"]:focus,
input[type="password"]:focus,
input[type="search"]:focus,
input[type="url"]:focus,
textarea:focus { border-color: #2B797C;}
.social-links ul a:before, .footer-widget-area button { background-color: #74CCD1;}
.site-info a:hover { color: #74CCD1;}
.footer-widget-area a:hover { color: #297679;}
Let me know how it goes. If you need further help, could you provide a link to your site so we can have a look directly and see exactly what CSS still needs tweaking?