Fly-spell mode and trunk

[Angelo Graziosi]

I have seen that on trunk recently (say at least with revision 112101) 
fly-spell mode changed the way to flag wrong word. Previously the wrong 
words become red or yellow (as in [*]), now they are just underlined 
(the underline looks very light, as in Libreoffice Writer or Thunderbird).

I wonder if one can restore the previous behavior (for example, in the 
Emacs initialization file, ~/.emacs, ~/.emacs.d/init.el). How?


TIA,
 Angelo.

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[*] http://www.webalice.it/angelo.graziosi/cygwin/emacs/emacs-mrxvt.jpg