If your using photoshop or a similar program, you can add texture to the water in a number of ways. The easiest is to simply create a cloud layer beneath your ocean layer and set the ocean layer to multiply or lower the opacity. (there are a number of great tutorials on this forum that will provide a number of different techniques...i'm also learning it so I might not be much help.)

A similar thing can be done to add color to your landmass. It would involve selecting the outline of those shapes and then filling them in a new layer with some color and then setting it to multiply. Again, lots of great tutorials.