1. Coated paper works great with the Sharpie markers. If you don't have access to any, try fingerpainting paper like this Strathmore type. Cut paper to 3.5" x 2.5" size. Draw outline of leaf with a black Sharpie marker.
2. Fill in the leaves with Sharpie brush markers. Color the background with a contrasting color.
3. Use a metallic markers like this Sharpie set to draw highlight colors on each card.
Note: I promise this post is not brought to you by Sharpie, they just happen to make markers that color really well.