Here are a few common reasons why someone might wrap colored electrical tape on the ends of a perfectly good extension cord:

To indicate a specific purpose: The color of the tape could be a code. For example, a red-taped cord might be reserved for a specific tool like a table saw, while a blue-taped cord is for a different purpose. This helps quickly identify and grab the right cord without having to trace it.

To mark voltage or rating: In a professional setting, colors are often used to designate a cord's voltage or ampere rating. Red might mean 220V, while yellow is 110V. This is a safety measure to prevent someone from plugging a tool into the wrong power source.

To differentiate ownership: If multiple people are working on a project or sharing equipment, each person can use a unique color of tape to mark their cords. This simple method prevents mix-ups and makes it easy to spot who owns what.

To signify length: The color could be a quick visual cue for the cord's length. For instance, a long 100-foot cord might have blue tape, while a shorter 25-foot cord has yellow tape. This saves time when you need a specific length for a job.

Without more context, it's impossible to know the exact reason, but these are the most common scenarios.