Solid gold jewellery rarely turns skin green. The green mark people sometimes see comes from copper in the alloy reacting with sweat, lotion or acidic skin chemistry, and the higher the gold content, the less copper in the mix.
18k gold (75 percent gold) is the least likely to react, 14k (58 percent) sits in the middle, and 9ct (37.5 percent) has the most alloy content and the highest chance of reaction. Gold plated jewellery turns skin green far more often, because once the thin gold layer wears, the brass or copper base metal is in direct contact with skin.
Rose gold uses copper to create its warm tone, so it can mark skin more than yellow gold at the same karat. If a piece marks your skin, the alloy or plating is reacting, not the gold itself.
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