Today's technique is this marbled bridge by Scott Stasiuk on Flickr, which stands out from regular bridges for a number of reasons. Check out the post here: https://www.flickr.com/photos/87637599@N04/42807141881/in/photostream/
Firstly, the bridge has a marbled texture because of the parts used by Scott. He uses a variety of textured pieces such as 1x2 masonry bricks as well as 1x1 studs.
He also marbles the bridge using colours such as tan and olive green to show wear and erosion of the structure.
This is a technique you can easily implement into your MOC, just be changing out regular bricks for a couple of different coloured plates and studs.