Comment 13 for bug 174720

The black box after ungrouping still remains. This is because the box had inherited the fill:none from the parent group, and specified no fill itself. When the group is gone, the box has no ancestor specifying its fill. Therefore the default value applies, which is black fill <http://www.w3.org/TR/SVG11/painting.html#propdef-fill>.

If you consider Inkscape a drawing application, and the <g> element a simple grouping of children, then this behaviour is indeed a bit surprising. If, on the other hand, you consider Inkscape an SVG editor, and the <g> element as a full-featured part of the inheritance hierarchy, then this is exactly the kind of behaviour one would expect.

I tend towards the latter, thinking more in terms of SVG structure than visual interface. I'd definitely want to keep current behaviour. However, it might become one of several options. There might be a command to "ungroup objects and merge attributes into individual objects", setting all style attributes that are inherited from the group object that is about to be deleted. One could argue whether merging styles like font makes any sense for children that are e.g. paths. Anyway, this would be a new feature, and should probably be discussed in an appropriate feature request. Not a bug here, as it's not related to currentColor.