| Horizontal voice cables | Blue |
| Inter-building backbone | Brown |
| Second-level backbone | Gray |
| Network connections and auxiliary circuits | Green |
| Demarcation point,telephone cable from Central Office | Orange |
| First-level backbone | Purple |
| Key-type telephone systems | Red |
| Horizontal data cables, computer & PBX equipment | Silver or White |
| Auxiliary, maintenance & security alarms | Yellow |
