Here’s is the code to change in your CSS –
.menu-toggle,
.sub-menu-toggle {
background-color: transparent;
border-width: 0;
color: #fff;
display: block;
margin: 0 auto;
overflow: hidden;
text-align: center;
visibility: visible;
}
This code is located in your style.css file. You can change it directly, or if you would like to keep your customizations separate then you can add this code in your Custom CSS by going to “Appearance > Customize > Additional CSS”. Just change the color: #fff;
to whatever color you prefer.
Let me know if that helps