Help with plotting mask and ROIs in one image

Greetings,

I’d like to find a programmatic way to plot my hippocampal slab (with maybe increased transparency) while also highlighting my ROIs. Is this possible using nilearn?

My intermediary solution is to highlight these separately as shown using plot_roi, but I think it would be more elegant to be able to “merge” these two figures (sagittal slab and sagittal ROI).