Game Boy Advance starting up in black and white

Try reopening it if there are any ribbon cables make sure they’re in all the way

I had the same issue recently and learned how to fix it by luck. Hold your finger over the touch sensor that changes brightness and then hold either start or select, it may take a few seconds but the color will turn back on. It can also be done again to make it black and white again. Sometimes I have to try it a couple times too, but it always works for me. Hope this helps😸

It sounds like your Game Boy Advance might be having a bit of a glitch. One thing you could try is checking the batteries or power source to make sure everything's connected properly. Sometimes that can cause weird issues like the screen going black and white.

If that doesn't do the trick, diving into some forums or tutorials online could be a good next step. I stumbled upon this helpful thread on https://guidedhacking.com/forums/gamephr... that might have some useful tips: GamePhreakers Game Modding Tutorials. They often have solid advice for fixing tech stuff like this.

I hope one of these suggestions helps you get your Game Boy back to full color soon!