Does anyone know what gauge wire is used for operating accessories and track signals. Please message me back at email@example.com
In general, since you didn't specify anything in particular, I'd use 24 AWG wire. You could go smaller for things like LEDs (28 - 30 AWG) but solenoids require something larger.
Telephone wire works good for signals. It even has color coding. Green Yellow, Red and Black for common.