I went with a diamond, though I really like your emerald as well. Try them both on, then you will know for sure. As for stone colorings, you can fine a range of shades in naturally mined or lab created. Lighter doesn't always mean mined and darker created. Also, lab created is not the same as synthetic or fake. Lab created gems are the same minerals as the mined ones, the formation process is just sped up in a controlled laboratory setting, hence the clearer, less included stone.
Princess Diana's engagement ring was a sapphire and diamond ring.