I have spreadsheets where 5 cells have general titles and have
different background colours. In other sheets, dozens of cells list
topics and are also colour coded to show which general title they refer
to.

I need to tabulate information so that a row would contain three cells:
the general title, a topic and data about it.

Is there a command that returns the colour of the cell background, so
that I could use this to select the correct title to accompany the
topic?