This is because user wanted to add City Gas plumbing as a color.

Until V19, the tabs and colors were fixed and part of the settings (hence the preferences screen), so, if the color of your electrical tab was green, for example, all the elements in the electrical tab were green.

Starting with V20 we have the Draw Styles Tab (outlined in red in the image below).

There are several default styles that you can change or add your own (Draw Styles button, outlined in green in the image below).

If you prefer, you can select each element individually and change the colors and styles of the lines, fillings, patterns, as well as texts (pointed with blue arrows in the image below