there are several ways, you can take your ink pads and "squish" them to get some ink on the lid and take a brush and some water and use the color from the lid and water color with that, or use your reinkers and put it on the lid, you can water this down a bit cuz it will be very dark, or you can buy the water color pencils and color in parts of the image then blend with a brush. OR some people color a circle on a scratch paper, then with a brush with water then watercolor on the image. OR you can purchase watercolors. I have a very expensive set from when i was in college and took a Watercolor corse. OR you can purchase the one of the waterbrushes!
Be sure to practice a few times!!
And remember watercolors look best if you dont make them look "perfect"
HTH
Christy