In dense fog, which fog lights is a passenger car required to use?

FRONT FOG LIGHT: - Its installation and use is NOT mandatory. - It shall be white or selective yellow in colour. - It shall be used, voluntarily, in the case of fog, heavy rain, snowfall, clouds of smoke or dust, or in circumstances similar to the above. - It may also be used on narrow roads with many bends, that is, those with a carriageway of 6.5 m wide or less, signposted with 'dangerous bends' signs. REAR FOG LIGHT: - Its installation and use is mandatory. - It shall be red in colour. - It shall be used, mandatorily, in the case of THICK or DENSE fog, VERY heavy rain, HEAVY snowfall, or DENSE clouds of smoke or dust. The front fog light, during the day, may be switched on with only the position light, but may also be used together with the low or high beam. At night, it shall be used at a minimum with the low beam. The rear fog light, during the day, shall be used at a minimum together with the front fog light or the low beam. At night, at a minimum with the low beam. The front fog light is not mandatory to use in any case; at the front, the vehicle may travel with low or high beam headlights.