Heartland

If I have interpreted colours correctly, it's a very violent song.

You reap what you sow = Self explanatory Bible quote.
Put your face to the ground = This is the most violent lyric, it puts an image in my mind of Andrew pushing Waynes face to the ground.
Here come the marching men = Eldritch, Ray & Vega are the marching men. I get images of Eldritch holding Wayne down and Ray & Vega stomping on his head.
Your colours wrapped around = The colour being blood red and wrapping around the feet of the marching men as they crush Wayne under their feet, charming.

It's a very violent song, but only metaphorically. Basically, it's Eldritch telling Wayne he is going to get annihilated once he releases his Flood/Gift.

Put your face to the ground always seemed to me to be a reference to an American Indian tracking technique where they press the side of their heads against the hard earth, since sound resonates through it more quickly and clearly than through air. As for the Colours, I'd imagine that to be a reference to military colours (i.e. the decor of a particular regiment).