In this awesome instructable I'll show you how to make a pixel art my way (the easy way)
I used Adobe Photoshop CC
After creating the document open the reference image in a new window.
Use the pen tool with 100% hardness (opacity also 100%) and with 1 pixel.
Also create 2 new layers, use the first one to draw the foreground(sand) and the other layer for the background(sky).
The easiest way to get the right colors is to use the color picker.