TSA X-ray scanners use a specific color-coding system based on the atomic density of materials to help officers identify threats. Orange represents organic materials, which include carbon-based items like food, paper, clothing, and leather; most "safe" items in your bag will appear in shades of orange. Blue or Black indicates inorganic materials and dense metals, such as keys, coins, wires, and—critically—knives or gun components. Green represents "mixed" materials or medium-density items that contain both organic and inorganic elements, such as certain plastics, glass, or complex electronics like a laptop’s internal circuitry. In 2026, newer CT (Computed Tomography) scanners provide 3D images that allow officers to rotate the view, but the core color logic remains the same. If an item is too dense for the X-rays to penetrate (like a thick block of lead or heavy machinery), it will show up as a solid dark mass, which almost always triggers a manual bag inspection because it can be used to "shield" or hide other prohibited items.