krcp Hi
You're right, the trigger button is set with that primary color, you can override with this custom css rule:
#t4-header .header-top .container .row #triggerButton>span, #t4-header .header-top .t4-masthead .t4-masthead-detail .row #triggerButton>span, .t4-masthead #t4-header .header-top .t4-masthead-detail .row #triggerButton>span {
color: #333 !important;
}
and change to your desired color.