I’ve been writing my gameboy emulator in rust and I had a lot of issues getting this startup screen to display properly, later I’ve realized it was achieved using the clever pallet swapping in runtime.

For pokemon red, the start screen flashing start is made possible by changing palette during runtime.

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let palette_num = if sprite.use_palette_1 {
                            self.op1
                        } else {
                            self.op0
                        };

By changing the pallet from op1 to op2, we are able to achieve that.

The emulator project (poorly written), can be found here