Allow legend label text color to be set per-layer/per-group

[Alex-Kent]

Feature description

It would be nice to be able to set the text color used for specific layers or groups in the Layers panel (Legend). This is useful when one has a lot of [categorized] layers open and one wants to tell them apart at a glance; currently all categorized layers are displayed the same (black text, grey blob icon).

Here's an example showing the issue, each of the categorized layer's has a different basic color set in its symbology but there's no way to tell them apart without expanding the legend (as with the 4th layer shown):

I propose:

• Add a setting to Layer→Properties→Legend that allows a color to be chosen.
• Update the code for the Layers panel to use the custom text color if one is set.

If a layer is selected then the text color could be used as the highlight color (thus ensuring legibility). The layer-specific text color could potentially also/instead be used to color the layer's icon/icon background (for e.g. categorized layers), perhaps this could be an additional per-layer setting. As layer groups don't have a properties dialog it might not be easy/practical to do this for them (though adding an entry in their right-click menu to set the color would be one way to do it).

Additional context

No response

[agiudiceandrea]

@Alex-Kent, have you already seen https://plugins.qgis.org/plugins/layer_color_plugin/?