+1  A: 

I think you are doing it wrong. I mean using taxonomy wrong, not technically, but as a concept. Ask yourself why do you have 2 vocabularies with term yellow? Both are colour. they belong to same dictionary. Maybe tell little more of what you are trying to make.

Maybe you need to change setup so you don't associate one dictionary to one content type, maybe CCK, views and this module can do what you need http://drupal.org/project/content_taxonomy

henrijs
That's a good point. The challenge came around because I imported some Wordpress blogs into Drupal, and the import module created two Taxonomies (one called Categories and another called Tags). But I am also thinking of adding Tags to the blog node that I create which could have terms that are the same as from the imported Vocabulary. And I want to make sure that if a term in one my tags is chosen the other imported nodes will also show up. But I do understand your point.
DKinzer
maybe taxonomy manager module can help you manage or migrate and fix those tags and categories, but i don't remember if it worked across dictionaries
henrijs