Use alt icon for selected "user flag" menu option

[lederer]

When the user taps the "user flag" menu, if one of the items is selected, we highlight it.

The original design called for inverting the colors:

That proved non-trivial, so we just change the foreground color. However, it can be hard to distinguish blue the color:

A straightforward solution would be to swap the icon for an inverted treatment. Like this: