It seems like the most obvious colonies are Hawaii for California and Cuba for Texas. Based on OTL they probably wouldn't remain colonies indefinitely though. If you want more, that will be difficult.
The Oregon territory is a possible avenue for expansion for California, but it really is limited to the pacific. Maybe the Philippines, or some other part of south east asia or indonesia, but I doubt it. At the time there was an opportunity to expand via economic deals, like singapore, California didn't have the kind of organization needed. Later when they had more people and infrastructure they still would be lacking compared to OTL USA, so I'm not convinced they would have the necessary power projection.
Mexico is a possible place for expansion for both, especially if they work together. But again, that is territory that will simply become more states, if they can hold it. Texas does have a few more options for expansion, but honestly, they all seem like awful choices. Haiti would be generations of rebellions and gruellias, and anything in Africa during the scramble would strain their power projection to the point that any of the European empires could just snatch it up. Maybe central america? Go Knights of the golden circle, and try and turn the carribean into a slave lake. Without the rest of the south/CSA I doubt it, even with it I still doubt it.