Highlight a row where a value changes relative to previous row (Conditional Formatting?)

What you suggest should work in combination with the right "applies to" range. For example if your data is in A1:C7 (with headers in A1:C1) then :

• select the range without headers, i.e. A2:C7

• use that formula (with preceding =), i.e.

  =$C1<>$C2

• apply required format

That should format rows 2, 4 and 7 as expected

...but I note your comments about deleting rows so this version will combat that while not "hardcoding" the column letter

=INDEX($C:$C,ROW())<>INDEX($C:$C,ROW()-1)