Dark Green (#013220)

/* Background */
.element {
    background-color: #013220;
}

/* Text */
.element {
    color: #013220;
}

/* Border */
.element {
    border: 1px solid #013220;
}

/* Linear gradient to complementary */
.element {
    background: linear-gradient(
        to right,
        #013220,
        #630125
    );
}

/* Radial gradient */
.element {
    background: radial-gradient(
        circle,
        #013220,
        #630125
    );
}

// SCSS variable
$dark-green: #013220;

// With RGB channels (useful for rgba() usage)
$dark-green-r: 1;
$dark-green-g: 50;
$dark-green-b: 32;

// Usage
.element {
    background-color: $dark-green;
    color: rgba($dark-green-r, $dark-green-g, $dark-green-b, 0.8);
}