Woodland Scenics has a couple of products that simulte water. One, you can pour from a bottle in the spot where you want it. Its best to do layers. Another is plastic pellletts that you melt than pour. I have both, but since I'm not ready for water yet, haven't tried any of them.
To color, since real water is actually clear, the beast thing to color is paint the bottom. Start out dark, like a black, and lighten it as you get closer to the banks with a brown or sand color. blending it with the bank.
Hope this helps.