Polygallon
Collision support is about as developed as it will get, I don't see any extra primitives being implemented for performance reasons. Collision "meshes" are too computationally expensive in JS, and wouldn't really be viable in a game. Already the collision system is difficult to get good performance out of, and it's pretty highly optimized with spatial hashing.
You can get away with compound objects if you need more complicated collision structures, but you'll have to set it up in construct for the regular colliders. The oimo behaviour however does support compound structures you can setup through events, although it can be pretty tricky to work out positioning the pieces at first. I've gotten chairs and tables and stuff to be built this way, and the capsule collider is actually a compound object as well!
In my latest build i've made small additions to the oimo behaviour so that you can check and retrieve information about the contacts / collisions, they should help if you need to retrieve things like penetration depth and normal etc.
Thanks for pointing out the color thing! must have slipped past me. three.js and construct use inverted RGB hex representations or something so this can annoyingly happen if i haven't explicitly fixed it. It used to be that ALL color setting actions had that issue.