[UmberGryphon]

I generally have pretty good luck waiting until the AI asks for a treaty (or until I think the AI would accept a treaty if I offered it one), and offering a trade--that treaty, in exchange for a colonization tech (or any other tech).

It values treaties way more than it values ANY technology, apparently. I've never seen it refuse a tech-for-treaty trade in a situation where it would accept the treaty.