Talk:Mettaton/@comment-96.5.246.38-20151019133624/@comment-26670176-20151019135232

After defeating Asriel (Pacifist Route), before going to the Surface, at Waterfall next to Mettaton's old house (next to Napstablook's, but I think only if you purchase the Mystery Key from Bratty and Catty), Mettaton should be in front of his house if you've befriended him, thus you can see his coloured sprite.

I think also if you befriended him, if you quit the game and look at your save file, his colored sprite will also be there.