One of the considerations one should keep in mind is in what context will this graphic appear. Is it a logo that will be placed on signage, bill boards, the web, maybe t-shirts? Should it convey the steadfastness of government, the dawn of the future, or a “Blast from the Past”?
The initial image can be done in black and white so the overall concept can be seen and modified more easily; then when colors are introduced into the equation one can have a bit of fun experimenting with various color schemes. There are plenty of books on the market which offer samples of various contrasting, complimentary, primary, and secondary color palettes. Remember the adage: “Less is More”. You want people to not only identify the graphic visually but remember it as well. Make it unique so it will stand out from the rest.
Above all, try various combinations and mutations. Some will be hits, some will be misses; allow the color to enhance the graphic and allow it to stand out. Think of the color as the added spice, and it holds the same as with food; too much spice can over power the meal, just the right amount can make it memorable!