private function generateColoursSetCode() : void
    {
        if (!ctype_digit($this->fg)) {
            $fgCode = self::$availableForegroundColors[$this->fg];
        } else {
            $fgCode = sprintf("38;5;%s", $this->fg);
        }

        if (!ctype_digit($this->bg)) {
            $bgCode = self::$availableBackgroundColors[$this->bg];
        } else {
            $bgCode = sprintf("48;5;%s", $this->bg);
        }

        $this->coloursSetCode = sprintf("\033[%s;%sm", $fgCode, $bgCode);
    }