If you are using fresh coconut milk, you can refer to the link given in the post. You may need to use a little more than one whole coconut for the milk.
I used coconut milk powder - prepare as per the instructions on the packet.
If using canned coconut milk, use one whole canned coconut milk (400 ml). Shake well and reserve 1/2 cup for the last. To the remaining, add water to make it 2 cups and use as thin coconut milk.
The color of the ada pradhaman will solely depend upon the jaggery used. Try to use the dark one (karupetti) for maximum color.