Turquoise Blue (#00FFEF)

/* Background */
.element {
    background-color: #00FFEF;
}

/* Text */
.element {
    color: #00FFEF;
}

/* Border */
.element {
    border: 1px solid #00FFEF;
}

/* Linear gradient to complementary */
.element {
    background: linear-gradient(
        to right,
        #00FFEF,
        #FF0010
    );
}

/* Radial gradient */
.element {
    background: radial-gradient(
        circle,
        #00FFEF,
        #FF0010
    );
}

// SCSS variable
$turquoise-blue: #00FFEF;

// With RGB channels (useful for rgba() usage)
$turquoise-blue-r: 0;
$turquoise-blue-g: 255;
$turquoise-blue-b: 239;

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