Unfortunately, it was the unsupported closed source coolcv, but it worked great, and was easy to integrate into emulation station. I was also able to get Shea Silverman’s old build of advmess to run Colecovision, but with issues, not recommended. I’d think that a new build of libretro mame/mess build would be the ideal, however lr-bluemsx and lr-fba might alternatively be able to do it. I know for sure bluemsx can run it, I’m just not sure if/how to do it in RetroPie.