One of the coolest color tricks that can be done with a digital camera and a flash is called white balance color shifting. As I learned back when my wife was wedding dress shopping, there are all different shades of "white." People's brains tell them that which ever shade they are looking at is actually white, but digital cameras are not that smart and use a setting called "white balance" to reference what part of a photo is actually white. This is greatly effected by the lighting used to illuminate what is in the photo.
White balance shifting is intentionally altering what the camera thinks is white for effect. In this case, incandescent lights like the ones outside (and inside) the house are much more amber in color than the sunlight which is lighting the light blue sky after sunset. I set the camera to display the light bulbs as white which then shifts all the colors in the photo to the bluer side of the spectrum, giving the sky that dramatic deep color. I gelled the flash to a warm color to match the light bulbs (actually even a little warmer than that so the house doesn't look white) and used it to light up the front of the house.
I was hurrying to get this done before the sunlight had completely disappeared and I probably could have up-ed the flash power to light up more of the house.... oh well, next time.