Which layer is primarily concerned with the properties of a card that affect its power and toughness?

The correct answer is Layer 5, which is primarily concerned with the properties that affect a creature's power and toughness. In the context of Magic: The Gathering, layer 5 is where various effects that set or modify the power and toughness of creatures are applied. This includes effects from spells, abilities, or static modifiers that do directly change the base statistics of a creature.

Layer 3 deals with colors and card types, which are important characteristics of a card but do not influence its power and toughness. Layer 7 is where effects that apply after power and toughness changes occur, such as counters and certain effects like "destroying" a creature, but it does not directly modify the numerical values of power and toughness. Layer 1 covers the card's characteristics such as name and whether it is a creature, artifact, or other types, but again, it does not affect power and toughness.

Understanding these layers is crucial for correctly determining how power and toughness can be modified during the game.