There are new and old Colecovision emulators. Quite frankly it been a crap shoot to track down really good ones. i'll be updating this page as things shift around with compatibility and such.
CoolCV by nanochess - This is by far the most compatible of all the emulators. It supports large ROM files as well as Super Game Module titles. Try it out! You can take PNG screenshots, and record gameplay video. Excellent overall.
BlueMSX by Daniel Vik - This emulator also emulates the MSX computer from Microsoft as well as the Colecovision.
There are many other Colecovision emulators out there, but quite frank the support on them has stopped. The two above are your best bets.