Jmol

Jmol is a Java-based molecular viewer.
The home page is http://jmol.sourceforge.net.
It can be downloaded from there.
You run the program by simply clicking on jmol.jar.
It is mostly fully intuitive.

Change background colour:
Archive–Console
write in the console:
background white

Render in POV-ray:
Click on Icon or Archive–Export–POV-ray
Ensure that the povray program is installed (and give the absolute path):
brew install povray

Create or delete bonds:
write in the console:
connect 3.0  (_CU) (_N) create   # creates bonds between Cu and N shorter than 3.0 Å