One citrus acid ester that can be used in color flame candles is **citrus terpenes**, such as **limonene**. Limonene is derived from citrus fruits like oranges and lemons and is known for its pleasant aroma. When combined with certain metal salts, it can produce colored flames.
For color effects, specific metal salts are typically added to candles, such as:
- **Strontium salts** for red flames
- **Copper compounds** for blue-green flames
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