I think what you need is:

#main{

background-color: #eee;

}

for site background color

p {
        color: #777;
}

for site font color

.bigger, .bigger p {     color: #222; }

h1, h2, h3, h4, h5, h6 {     color: #000; }

for header colors

#header-container {
    background: #fff;
    border-left: solid 1px #eee;
}

for sliding menu header background color

hamburger span::before, .hamburger span::after {
    background-color: #000;
}

.hamburger-rotate {
    background-color: #fff;
}

.hamburger-rotate.is-active {
    background-color: #fff;
}

.hamburger span {
    background-color: #000;
}

.hamburger span::before, .hamburger span::after {
    background-color: #000;
   
}

for the menu. replace the colors with your values and add the code to theme options -> styling options -> custom CSS