I divided the different colours by using bold black lines. They made it very easy to identify the different shapes.
I have done darker colours for the river and lighter colours for the sun. It creates impact.
I used different tones in my river the most but i also used tones on my hills and sun. It makes the river stand out more.
I used a circle for the sun and wavy lines for the hills, river and streaks coming out of the sun. They are bold shapes they stand out.