Outside of color images, National Geographic uses only 2 colors: black and a goldenrod yellow.
Each cover is edged with a yellow frame, which gives the publication a vintage look, draws the eye to it sitting on a shelf, and carries the eye to the cover photo. The yellow frame is an element that is noticed but quickly disappears in lieu of the dynamic cover images.
Headlines, subheads, display text is always black or white, body text is black, and the yellow is used as an accent. Though used sparingly, the yellow adds dimension to the page.
The yellow is also used for color blocking, which adds more to the vintage aesthetic.
Minimal use of color allows National Geographic to highlight profound images without solely relying on the images to provide color. Splashes of yellow draw the eye but to not hold it, allowing the eye to follow the hierarchy naturally.