Router fiber optic cables are not typically red; red usually indicates backup or special-purpose fibers.

Fiber optic cables follow standardized color codes to identify fiber type, purpose, and position within a cable bundle. According to international standards like TIA-598-C, single-mode fibers often have yellow or blue jackets, with green for APC connectors, while multi-mode fibers are usually orange, brown, violet, or aqua. Red and black are generally reserved for backup or special-purpose fibers, not standard router connections . The color of the cable jacket or individual fiber does not indicate the router's operational status. For example, a red LOS light on a router signals a loss of signal, not the cable color itself . Fiber optic cables can be manufactured with custom jacket colors, so the physical cable connected to your router may vary depending on the provider or installation, but red is uncommon for standard active connections . In practice, the most important aspect is ensuring the fiber is correctly connected to the router's WAN or ONT port and that the fiber type matches the network requirements. The color coding mainly helps technicians identify fibers during installation, maintenance, or troubleshooting, especially in high-density setups .