This is an attempt to provide an attendance form for completion at a
meeting. Currently a hard copy is printed, the record is made by pen
or pencil, a mark to show who is present, and then I have to enter
the results into my spreadsheet.

Is it possible to apply conditional formatting to the cells so that a
click changes the content of the cell between two states?

One state being default "Absent", (by colour if needed), and if the
cell is clicked the member is shown as being present, (by showing a
different colour), another click returns the cell to the default
state.