Which wood layer is typically lighter in color than heartwood?

Sapwood is the correct choice because it refers to the outer layers of wood that are still active in the transport of water and nutrients from the roots to the leaves. This part of the tree is generally lighter in color compared to heartwood, which is the innermost, older, and typically darker portion of the tree. Heartwood is formed as the tree matures and the sap channels within it become filled with various deposits, giving it greater density and darker colors.

Bark, while important for protecting the tree, is not a layer of wood and does not engage in the same processes as sapwood and heartwood. Veneer refers to thin slices of wood that are typically sliced from logs and used for surfaces or finishes, so it doesn't represent a natural layer within the structure of the tree. Therefore, sapwood stands out as the layer that is lighter in color compared to heartwood.