Two correct conditional-formatting rules can compete for the same Calc cell. A broad rule may match before a more specific one, so the colour you expected never appears. Inspect the rule list before repainting cells by hand.

First select one affected cell and record its actual value, the formatted range and the intended meaning of each style. A colour rule is a presentation instruction; it does not correct the value or establish that the underlying measurement is reliable.

Test an overlap with known values

In a small example, suppose values above ten should be amber and values above twenty should be red. The value twenty-five satisfies both conditions. If the above-ten rule is first, Calc applies that first matching style, leaving the more specific red rule unused for the cell.

Open Format, Conditional, Condition and inspect the ordered list. Move the specific above-twenty condition ahead of the broader one using the priority controls. Confirm that the range includes the intended cells and does not include an unrelated totals area.

LibreOffice also requires AutoCalculate for conditional formatting. Its Data, Calculate menu shows whether that option is enabled. Record the existing state before changing a workbook that someone deliberately calculates manually.

Include boundary and no-match cases

Test values ten, fifteen, twenty and twenty-five. With strictly greater-than conditions, ten matches neither rule, fifteen and twenty match the amber rule, and twenty-five matches red. If the requirement instead includes a boundary, change the condition deliberately and update the expected results.

Inspect a cell that matches no condition. Calc retains underlying manual formatting and cell styles; those can reappear when conditional formatting no longer applies. A remaining fill colour therefore does not necessarily mean the conditional rule is still true.

Restore the real values after the disposable test and check the first and last cells of the production range. Keep a written legend that explains the thresholds without relying only on colour. The result should be a predictable mapping from values to styles, including overlaps and boundaries, rather than a sheet that merely looks correct for today's sample.

Reference: LibreOffice documentation.