Fix wrong usage of color identifiers.

            color: get-color($color-name, $i)

// Add black and white.

@each $color in black, white

    .bg-#{$color}

        background-color: $color

    .fg-#{$color}

        color: $color

    .bg-black

        background-color: black

    .fg-black

        color: black

    .bg-white

        background-color: white

    .fg-white

        color: white