Why add Wheat Germ to Bread?
Wheat germs are the repoductive parts of the wheat grains. Like all germs, they are rich in vitamins, nutrients and oils. The oils are the reason the germs are removed during the milling process: they can become rancid quickly and reduce the shelf life of the flour. In whole wheat, the germ remains included, hence the shorter shelf life.

But the germ is not what makes the bread "dark", that's the outer bran - also removed during milling for white flour. Your recipe uses whole wheat flour, which explains the "dark" in the name.

In your recipe, I assume the wheat germ is included to make the bread "healthier" - like in many totally different recipes that use it. It may also influence the taste with "nuttier" tones and a tiny bit the texture. But combined with whole wheat flour, the effect is limited.