You're very close! The "seas" of the moon are dark because they don't reflect as much light, but it's not about a specific range of light. Here's a breakdown:

* The "Seas" are actually plains: The lunar maria, or "seas," are vast, dark plains of solidified volcanic basalt.

* Basalt is dark and smooth: This type of rock is naturally darker than the surrounding lunar highlands, which are made of lighter-colored anorthosite. The smoother surface of the maria also reflects less light than the more textured highlands.

* No water, no reflection: The term "sea" is a misnomer. There's no water on the moon, so it's not about reflection in the way we think of it with water.

In essence, the maria appear dark because their composition and surface texture reflect less light than the surrounding lunar highlands.