I realized I only build in muted colors so I figured I'd break the trend and make something a bit more colorful. I even tried to carry the colored stripes through from front to back. I reserved the grey for more mechanical and motor/generator type parts. I even put some traditional exhaust pipes and a sensible double-barreled cannon.
Wow! How have I missed this? A riot of colours but done in an organised way to great effect. I like how you've used the grey for functional parts, as you mentioned, such as the engine thing on the back. As this has weapons, I assume that this colour scheme is camouflage: imagine what the planet must look like! Great fun.