Dark Olive Green (#556B2F)

/* Background */
.element {
    background-color: #556B2F;
}

/* Text */
.element {
    color: #556B2F;
}

/* Border */
.element {
    border: 1px solid #556B2F;
}

/* Linear gradient to complementary */
.element {
    background: linear-gradient(
        to right,
        #556B2F,
        #5B2FA7
    );
}

/* Radial gradient */
.element {
    background: radial-gradient(
        circle,
        #556B2F,
        #5B2FA7
    );
}

// SCSS variable
$dark-olive-green: #556B2F;

// With RGB channels (useful for rgba() usage)
$dark-olive-green-r: 85;
$dark-olive-green-g: 107;
$dark-olive-green-b: 47;

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