For many years I used tea leaves in my plants. From experience, I can say it enhances the colors of the leaves and also grow very rapidly.
Step 1: How I Do It.
After making tea, I soaked the used tea leaves in water and then water my plants with it. It enhances the color of the leaves.
The "used tea leaves" can also be used as compost. But it is not advisable for indoor gardening as it attracts mosquitoes. It can be used in garden though. I have been doing this for a long time now and it works great :).