I have an idea for a different kind of clock but the arduino Uno or Mega does not have enough pins. This clock will need 48 individually addressable red LEDs plus 12 individually addressable RGB LEDs. Because more than one LED may be on at any given time, I’m not sure that I could charlieplex them. Anyone have any suggestions that may help me?
Have you had a look at shift registers? If you chain 6 shift registers together, that will take care of your 48 red LEDs using only 3 Arduino pins. They are cheap and pretty easy to use - just make sure you use a socket rather than trying to solder them directly. I also add a bypass capacitor.
Then drive your 12 individually addressable LEDs from the remaining Arduino pins - I assume they only need 1 or 2 pins?
Why can't you just use a WS2812 strip instead of individual led's?
You could some port expanders eg mcp23008 to extend the number of ports you get on an Arduino. You can use up to 8 of these together over I2C.
Some port expander solutions are limited ( eg pcf8574 can only sink current), so read the data sheet carefully.
A single MAX221 can handle 64 LEDs and takes four Arduino pins. Maybe that will do.
Some good suggestions. Certainly food for thought!