Grid color issue with palette

[PhoenixFnX]

Hi,

Bug Description
If I do this :

        $palette->majorGridColor = '#000000FF';
        $palette->majorGridColor = '#000000aa';
        $graph->palette = $palette;

then my graph has a major grey grid on xAxis (vertical lines) and yAxis (horizontal lines).

But if I do this :

        $palette->majorGridColor = '#000000FF';
        $graph->palette = $palette;
        $palette->majorGridColor = '#000000aa';

then my graph only has a major grey grid on yAxis (horizontal lines) only.

Questions
To sumarize, is the palette still writable after setting it to the graph ?
If I want to apply a slight palette modification on a specific Axe, do I have to clone it ?

Usecase
Actually my objective was to get only the vertical grid. This is what I did :

            $palette2 = clone $graph->palette;
            $palette2->majorGridColor = '#000000aa';
            $graph->xAxis->setFromPalette($palette2);