Tool Box colors can be customized according to your preference. Whenever you leave a note, that note defaults to a red color. But, in that same toolbox, you can change the color to any color that you desire. You can devise your own system of what each color means.  There are only two fixed colors - red is the default color for a note and the gold color alerts you to any 'public' notes that someone in your company wants to share. You can choose to make a note public or private.
You can retrieve notes of any color and see other toolbox functions by clicking on the toolbox tab.
For more clarity, please refer to the video below:
Toolbox Color Codes