a modified Adafruit library for the IS31FL3731 made to work with the Pimoroni 5x5 RGB LED breakout board
-the real work in modifying was done by u/Jasonic8
I got their files from here: https://drive.google.com/file/d/1i2ZUfTKgYsResBc5dZn-SBu3Qsc7nwkl
example sketch attached is also Jasonic8's work
and of course the original library is made by Adafruit
I just moved and modified some array declarations in the library code which didn't want to compile on my machine.
perhaps it will be a useful resource for someobody, as provided Pimoroni cpp examples were quite troublesome to use (I never did get them to work)