[Feature request] I think there should be an easy and straightforward way to change opacity in plotly express cloropleth maps

[Francesco-Ghizzo]

Many times in GIS and map visualization, it is useful to add a certain degree a transparency to a vector layer to see which features of the baseline map are covered by the tiles.
To my knowledge, there are options for selecting continuous and discrete color scales.
However, there isn't an option for removing the color altogether (visualizing only the vector borders) or changing the opacity of the color

[robertclaus]

We're working on a larger project to update how we handle colors, so we likely won't do a targeted fix for just this. We would be open to reviewing a community PR though!