How to control 8x8 rgb matrix with uno?
What about it ? You need 8*8*3 =192 I/O lines because it's a 3- dimensional matrix ( 8x8 red, 8x8 Green, 8x8 Blue). You need I2C I/O expanders because the arduino doesn't have enough GPIO. That's just the hardware. You haven't said anything about the software. Do you want 64000 colors too ? Have you tried to find one online ? WS2812 ?
While I would recommend a WS2812b strip of LEDs these days, this project is in essence a RGB 8 by 8 array, only arranged not in a square matrix. Schematics and software is download able from this page.
It uses multiplexing to reduce the number of signal lines required.