Short
The planet that changes colour (Mercury in Vedic astrology)
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Mercury is benefic alone or with benefics, but takes on the nature of the malefics it joins: read Budh by its company.
This video belongs with Budh (Mercury) in Astrology: Meaning, Myth, Dignity and Dasha, which has the full explanation and its classical sources.
Transcript
In Vedic astrology, there is one planet that changes colour. It is Mercury, Budh, the planet of the mind, speech and trade. Alone, or with benefic planets, Mercury is benefic. But joined with malefic planets, it takes on their nature. So when an astrologer reads your Mercury, the first question is: who is sitting with it?
See your Mercury, and its company, in a free kundli at sunyra.ai.
Astrology is a tradition of interpretation; read this as guidance, not a forecast. Disclaimer.