Electric Ultramarine (#3F00FF)

/* Background */
.element {
    background-color: #3F00FF;
}

/* Text */
.element {
    color: #3F00FF;
}

/* Border */
.element {
    border: 1px solid #3F00FF;
}

/* Linear gradient to complementary */
.element {
    background: linear-gradient(
        to right,
        #3F00FF,
        #FFFFFF
    );
}

/* Radial gradient */
.element {
    background: radial-gradient(
        circle,
        #3F00FF,
        #FFFFFF
    );
}

// SCSS variable
$electric-ultramarine: #3F00FF;

// With RGB channels (useful for rgba() usage)
$electric-ultramarine-r: 63;
$electric-ultramarine-g: 0;
$electric-ultramarine-b: 255;

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