One of several experiments with color I've been working on lately, derived from a color scheme challenge available on deviantart.  The selections vary from artist to artist, but the rules for the color challenge remain more or less the same across all variations. 

Long story short, the creator of the challenge gives you six sets of colors to work with; you must use each of those six sets to create an image, either pure (for a real challenge) or mixed (for those who like to slam colors together and see what happens).

I decided variant 1 would be the best choice, as color usage and lighting are two of my big weaknesses when it comes to devising concepts.  In keeping with this idea, I decided to extend the rules even further - on top of only using the colors assigned, each image must present a comprehensible scene, whether landscape- or character-oriented.  The result was a series of color sketches which I have been slowly converting to pixel-art form.

This particular palette consisted of five colors, all of them a variation on the theme of blue.  I tried to use the varied levels of brightness to create a contrast between fore- and background. 

Made in ASEPRITE.