Bear in mind that a schematic diagram is a simplified connection map, not a wire routing map. A few diagrams illustrate in detail where wires physically run throughout a chassis, but many lack that degree of clarity. In addition, the physical routing of some accessory wires may differ between years and even assembly plants, not-to-mention accessories that may be installed after factory at the dealer level. Suffice it to say that you are correct in deciphering that brown is tail/running and black is ground. You are also correct that the circuit 150 ground wire in the diagram is mislabeled as circuit 9, 0.8(mm)2, brown.