\cellcolor overwrites table lines

Please don't just post fragments of code that can not be run, always post complete small documents.

The fix should be exactly as in the other question. As documented colortbl is incompatible with \cline, you need to use \hhline instead. The fact that the cell backgrounds are different colours is irrelevant to the problem of \cline including negative spacing so that it comes under the colour.

Just put the command \cellcolor[]{} inside brackets {} and it will not overwrite the table lines like this

\hline

{\cellcolor[gray]{.8}} Chapter & Title \\

\hline