When choosing a concealer shade, it's generally recommended that the concealer should be slightly lighter than your foundation. The reason is that a lighter shade of concealer can effectively brighten and highlight the areas where you apply it. In the instance of concealing dark circles, it helps create a more lifted and awake appearance.\
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However, it's important not to go too extreme with the difference in shade. The concealer should still be close to your natural skin tone and not excessively lighter, as this can lead to an unnatural or overly highlighted look.\
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As with any makeup rule, individual preferences may vary, and experimenting with different shades can help you determine what works best for your specific skin tone and desired makeup style.