The Use of Color
Contrast, unity, and emphasis are all used in anime and manga, so here's another comparison, except it doesn't focus on specific color this time.
Screen caps on RESOURCES page
Shingeki no Kyojin (Attack on Titan)
This is a pomegranate. As you can see, it definitely catches your eye. The contrast between the red and the white is pretty high, therefor looking appealing to the viewer.
The emphasis is this picture would totally be the shines on each of the pomegranate seeds because it makes the overall seed pop out compared to anything else.
With all of these elements working together, it paints the picture of unity. The image is satisfying to look at, and that proves it.
Noragami
With this drawing, let's begin with the emphasis. The first place that caught your attention was the eyes, for sure. It's because of how bright the blue in it is compared to everything else, and partly because of the fact that it gives off the appearance that they're glowing.
Speaking of the bright eyes, this is an obvious sign of contrast because of how the blue in his eyes differ from the dark shade that is overlapping his face --making the eyes stand out from the rest of the picture.
As you could tell, everything in this piece is working together in harmony that visually looks good, creating unity. Although both of the images represented are different, they both display unity in the overall picture.