This is a reverse-engineered schematic for the ColecoRGB designed by CitrusPSI. A copy of the board can be ordered from OSH Park at https://oshpark.com/profiles/citrus3000psi

While this version claims to work only with PAL and is intended for use on the ColecoVision, it actually works with any TMS9928 or TMS9929, and in my opinion is a far superior design to the version which is intended for NTSC Colecovisions. The TMS9928/9 were used in a variety of other platforms such as MSX, TI-99/4, and even a number of arcade games. None of them are exempt from the RGB output that this board offers.

A newer alternative, the TMS-RGB, was created more recently, featured at https://tms-rgb.com/