Hmm, maybe metallic green or chocolate ones? The farm is quite bright, so some darker ants would be good, but it might be good to have ants that aren't too big like the dragons. That's up to you though, the blue dragons might look nice. I'd go with green or brown ants personally ^_^
And you can have an animation! I think that'll still cost really, since it's a lot more work than anything else available for the farms. I do wish it was easier, but what can you do ^_^'