Logos should be Iconic in nature... ideally they can be printed monochromatically.
The logo should be distinctive and instantly identifiable without any text.
The one MD posted is the only one out of all the submissions that really fits the bill, (could be better but it's the best one submitted IMO).
Think about automaker logos...
Dodge, Chrystler, Chevy, Mercedes, Honda, Infinity, Toyota, etc. etc. etc.
All of them can be created by painting a single solid form over another solid color.
You can then adapt it to 3D to give it some depth.
Some of them use more then one color like BMW or Ford but they're still very iconic in nature. which is why they work.
Some good logos:



And those can all be adapted but hold the same meaning:


