How do I dry Senna leaves to keep good green colour?

Green colour retention is what fetches the price for Senna leaf. Dry the leaves in shade with good air flow rather than harsh direct sun, since strong sun and over drying turn the leaf brown and drop the grade. Spread thin layers so the leaves dry evenly without sweating or moulding, and stop when they are crisp but still good green. Keep the leaf free of stem, dust and soil because clean, green, well dried leaf gets the premium and dusty mixed lots get downgraded. Store in clean dry bags away from moisture to prevent fungus and colour loss. Confirm the exact colour, moisture and cleanliness standard your buyer wants before drying the whole harvest.