Mobile Menu color in 7.1 template 'Almar'

Hi,

I want to change the background colour of the mobile menu bar in the 'Almar' template, but I can't change this. All the code on this forum does not seem to work. Can somebody please help me out? It seems that 7.1 has some flaws like not having the option to change this from the color menu.

The url is https://bassoon-carillon-s3hj.squarespace.com/, the password is Loremipsum1

Best,

Joel

Mobile header, mobile overlay or..?

@media screen and (max-width:640px) {
nav.header-menu-nav-list {
    background: red;
}
}