I would NEVER do a color coordinated or themed tree. That would be totally meaningless.
Instead, we buy a fresh NC Fraser fir and hang ornaments that we have collected throughout our lives together on it. A few new ones are added each year. Included are a couple ornaments we bought on our honeymoon, ornaments from trips to various places (We buy a new Disney one each year.), a first Christmas ornament with photo for each child, some things the kids made in preschool (not TOO tacky). We also have some Hallmark ornaments -- some with specific meaning and others that we bought just because we like them and a number of things we've received as gifts over the years. We give ornaments to each other and those go on the tree, too.
I also have a Hallmark miniature tree in the dining room. I really enjoy it, but overall it has less meaning because it's just Hallmark ornaments given to me by dh and the boys and bought after Christmas on sale.