Struggling to get consistent color output from my DIY LED matrix with Arduino

I've been working on a 16x16 RGB LED matrix powered by an Arduino Mega for a home project. The goal is to display smooth color gradients, but I'm running into flickering and inconsistent colors despite using PWM and the FastLED library. I've tried lowering the refresh rate and double-checked wiring, but the colors still don’t look stable when displaying complex patterns. Power supply is a 5V 10A adapter, so I think current isn’t the issue. Has anyone dealt with flickering or color instability on large DIY LED matrices? Could it be something in my code or hardware setup that I’m overlooking? Any tips on debugging color output consistency or alternative approaches to driving such a matrix would be super helpful.