How to reproduce :

• in your model, add a param css :

  .header{ background-color:#004C66!important /* AMETYS ("template.header.div", MODEL_HEADER_BGCOLOR) */; }

• add your translation in your model catalog :

  <message key="MODEL_HEADER_BGCOLOR">Couleur de l'entête</message>

  > the new parameter appears but it does not find the translation which it search it in the skin catalog.