1. Identify the type of stain - Different types of stains require different treatments.

2. Use a mild detergent - If its a grease or oil stain, use a mild detergent and warm water to clean it. Be sure to use a soft cloth to avoid scratching the surface.

3. Try a poultice - For tougher stains like ink or adhesive, try making a poultice. Mix a paste using baking soda and water, apply it to the stain, and cover with plastic wrap. Leave it overnight, then gently wipe off the paste.

4. Use a stone cleaner - If the stain is still there, try using a stone cleaner specifically designed for the type of stone in your honeycomb panel.

5. Avoid harsh cleaners - Also, avoid using anything too harsh or abrasive like bleach or acidic cleaners as it can damage the stone surface.

6. Get professional help - If all else fails, contact a professional stone cleaner who can assess the stain and recommend the best approach.