Trying to understand compilation error message
You are trying to use a library, but it is either not installed, or is installed in the wrong location. A library, in this context, is code that supports a sensor or some other hardware or that accomplishes a task. We call them libraries because we can share and reuse them – like borrowing a book from a library.

It looks like you're trying to get the Adafruit TCS34725 color sensor going. The official source of the library is in the Adafruit's GitHub repository for the TCS34725 and there is a link at the bottom of the README for how to install a library. I'll bet that will get you back on track.