Michael Andersen@HOT ML made a mapcss style for JOSM.

It can distinguish damaged/collapsed buildings. (damaged=green, collapsed=red) 

Here is [https://lists.openstreetmap.org/pipermail/hot/2013-November/003966.html Original Post], and on [http://wiki.openstreetmap.org/wiki/Damaged_buildings_crisis_mapping OSM wiki page].

{{{
meta
{
title: "Collapsed/damaged buildings";
author: "Hjart";
version: "0.1_2013-11-13";
description: "Style to classify buildings";
link: ;
watch-modified: true;
}

area[building=collapsed]
{
text: "collapsed";
text-color: black;
dashes: 20,4;
font-size: 10;
z-index: 1;
color: #FF2238;
fill-color: #FF2238;
width: 3;
}

area[building=damaged]
{
text: "damaged";
text-color: black;
font-size: 10;
z-index: 1;
color: #F5FF3B;
fill-color: #F5FF3B;
width: 3;
dashes: 20,4;
}

area[typhoon:reviewed=yes]
{
text: "damaged";
text-color: black;
font-size: 10;
z-index: 1;
color: #3CED28;
fill-color: #3CED28;
width: 3;
}

area[typhoon:reviewed=cloud]
{
text: "damaged";
text-color: black;
font-size: 10;
z-index: 1;
color: #3CED28;
fill-color: #3CED28;
width: 3;
dashes: 10,10;
}
}}}

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