This is a style to visualize the presence of some of the simple 3D building tags (i.e. building:colour, building:levels roof:levels) as well as certain building types, which can be obtained during ground surveys. Therefore, it helps mapping these tags from within JOSM faster and more efficiently because you can see easily where these tags are missing!

Please feel free to add ideas for further improvement at the bottom of this page.

meta   
{
        title: "Simple building tags";
        author: "heilbron"; 
        version: "1.21_2020-10-05"; 
        description: "Visualize the presence of some basic simple 3D building tags (wall colour, number of building and roof levels)";
        link: "http://josm.openstreetmap.de/wiki/Styles/SimpleBuildingTags";
        watch-modified: true;
}
        
       
area[building], area[building:part]
{
        z-index: 1;
        fill-opacity: 0.03; /* let the background, i.e. the roof, be recognizable through the background */
}

area[building]["building:colour"], area[building:part]["building:colour"]
{
        z-index: 1;
        opacity: 0.9;
        color: (tag("building:colour")); /* if a color is set, use it to color the outline ... */
}

area[building]["building:colour"=white], area[building:part]["building:colour"=white]
{
        color: #F5F5F5; /* ... but make a white boarder(#FFFFFF) a bit distinguishable from a white background */
}

area[building]["building:colour"=grey], area[building:part]["building:colour"=grey]
{
        color: #AAAAAA; /* ... but make grey (#BEBEBE) a little darker*/
}

area[building]["building:colour"=darkgrey], area[building:part]["building:colour"=darkgrey]
{
        color: #505050; /* ... but make darkgrey (#A9A9A9) quite darker*/
}

area[building]["building:colour"=brown], area[building:part]["building:colour"=brown]
{
        color: #802020; /* ... but make brown (#A52A2A) darker*/
}

area[building][!"building:colour"], area[building:part][!"building:colour"]
{
        z-index: 1;
        color: #202020; /* no building:colour tag => make the outline look almost black */
}

area|z17-[building][!"building:levels"], area|z17-[building:part][!"building:levels"] /* no building:levels set? => dash the outline */
{
        z-index: 1;
        width: 4;
        dashes: 3,3; /* any building WITHOUT a building:levels tag (except fpr garages) gets a 4 pixel outline */
}

area|z17-[building=~/garage.*/], area|z17-[building:part=~/garage.*/]       /* ... but almost ignore building tags for garages, i.e. make them all look the same */
{
        z-index: 0;
        width: 2;
        dashes: 8,1;
        color: #282828; /* garages get a thin, dashed, almost black outline, unless tagged otherwise */
}

area|z17-[building]["building:levels"], area|z17-[building:part]["building:levels"]
{
        z-index: 1;
        fill-opacity: 0.03; /* let the background, i.e. the roof, be recognizable */
        width: 5; /* any building WITH a building:levels tag (except for garages) gets a 5 pixel thick outline ... */
        /* text-halo-radius: 2; */  
        /* ... as well as a text tag giving the house number as well as the number of building:levels and roof:levels (and roof height in brackets): */
        text: eval(concat( cond(has_tag_key("addr:housenumber"), tag("addr:housenumber"), "."), " - ", tag("building:levels"), "/", cond(has_tag_key("roof:levels"), tag("roof:levels"), "") ,   cond(has_tag_key("roof:height"), concat("(",tag("roof:height"),"m)"), "")  )) ; 
        /* font-size: 9; */
        font-weight: bold;
}

Styles_SimpleBuildingTags-style.mapcss, Styles_SimpleBuildingTags.zip

Ideas for improvements:

• Visualize the number of building:levels --> added in version 4.
• Visualize roof:height in round brackets, too. --> added in version 11.
• Treat building:part's the same as buildings. --> added in version 12.