Getting term_id for newly created or edited term

Use the action created_term. Its first parameter is the $term_id.

It is called in wp_insert_term() in wp-includes/taxonomy.php after a term was successful created:

do_action("created_term", $term_id, $tt_id, $taxonomy);
do_action("created_$taxonomy", $term_id, $tt_id);

The second parameter is the term_taxonomy_id from the term_taxonomy table, and the last parameter is the taxonomy.

So register an action with …

add_action( 'created_term', 'wpse_78858_add_color', 10, 3 );

… and your callback should look like this:

function wpse_78858_add_color( $term_id, $tt_id, $taxonomy )
{
    # do something
}