Set Default value to Custom field (term to taxonomy)

Hello all,

I have few custom fields in the theme (Classifieds) – some lists, some taxonomies, some radio buttons. All taxonomies have values. When users open Add Listing page they see blank field and the list appears only when they click the combo box. I want to set default values to taxonomy fields such as “Pick your city name” in City field (taxonomy), “Choose you color” in Color field. “Pick your city name” and “Choose your color” are values (terms) in these taxonomies. Theme doesn’t have a feature to assign a default value to taxonomy.

Any one can share the knowledge or code?

Cheers,
Andrew