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What may cause the red color of Jupiter’s Great Red Spot?

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photo of Jupiter taken by Voyager 1 — Jupiter Photograph of Jupiter taken by Voyager 1 on February 1, 1979, at a range of 32.7 million km (20.3 million miles). Prominent are the planet's pastel-shaded cloud bands and Great Red Spot (lower centre).

The exact cause of the red coloration of Jupiter’s Great Red Spot remains unknown, as scientists have yet to reach a definitive conclusion.12

However, researchers have developed several viable hypotheses to explain this phenomenon:

Chemical Compounds: The color may be attributed to the presence of complex organic molecules, red phosphorus, or various sulfur compounds.12
Production Mechanisms: These substances could potentially be generated by high-altitude photochemical reactions or lightning discharges within the planet's atmosphere.12

While laboratory experiments have provided support for these ideas, each hypothesis currently faces counterarguments. The localization of this distinct color within the Great Red Spot—despite the presence of other cloud features across the planet—remains a subject of ongoing study in Jovian meteorology.2