Hey, thanks for adding destinations. Note that for the symbols, colours, etc. the :lanes comes at the end. I.e. destination:colour:lanes instead of destination:lanes:colour. I've fixed this here.

For future reference, you can test signs here:

http://osm.mueschelsoft.de/destinations/example/sandbox.htm#country=IT&tags=%20%20bicycle%20=%20no%0A%20%20destination:lanes%20=%20Autostrada%20A22;Autostrada%20A4;Mantova;Tangenziale%20sud;Aeroporto|Brescia;Trento%0A%20%20destination:colour:lanes%20=%20green;green;blue;green;white|blue;blue;brown;brown%0A%20%20destination:ref:lanes%20=%20A22;A4;;;|SS11;SS12%0A%20%20destination:symbol:lanes%20=%20;;;motorway;airport|%0A%20%20foot%20=%20no%0A%20%20highway%20=%20trunk%0A%20%20horse%20=%20no%0A%20%20lanes%20=%202%0A%20%20maxspeed%20=%2060%0A%20%20oneway%20=%20yes%0A%20%20ref%20=%20T4-T9%0A%20%20surface%20=%20asphalt

I do that a lot when adding destination tags, just to make sure the rendered sign bears some resemblance to the original.