The problem I see with pre-colored wires is that I will need an extra 30 feet of brown and all I have left is a small coil of orange. If it's all black, I can make it any color I want.
And to answer the original poster's question: roughly 3-4" of solid colored tape within an inch or so of the wire termination and another similar wrap of tape 18" to 2' away if it's in a place where it's likely I'll be tracing wires again such as within any controls for motor starters, lighting contactors, etc.
