In Google Sheets there is now the Alternating rows formatting. It's almost the equivalent of of tables in Excel.
Background
What if I have a sheet that is sorted by Invoice #'s, my unique number associated with a bill I send out to someone, but that someone breaks my invoices up into multiple line items associated with their own number called a Purchase-Order-Number.
Question
How do I Highlight every other invoice such that I can more easily distinguish which Purchase-Orders belong to which Invoices?
Additional Applications Any sheet sorted by a particular column whose values are not unique. For instance, if you have sales agents, and you want to highlight every other agent.