【C++/CLI】8Bitモノクロのカラーパレット設定方法

//8BitのBitmap作成
Bitmap^ bmp = gcnew Bitmap(pictureBox1->Width, pictureBox1->Height, Imaging::PixelFormat::Format8bppIndexed);

Imaging::ColorPalette^ pal = bmp->Palette;

for (i = 0; i < 256; i++){ pal->Entries[i] = Color::FromArgb(255, i, i, i);
}

bmp->Palette = pal;