If it's using that many unique colors, try using a palette used by something in the 2nd tileset for maps (palettes 8 - 12). The only thing is that you have to use that particular tileset for every map you want the house to appear in. If this is something you want to use in the 1st tileset, the palettes normally associated with those graphics are between palettes 0 - 6. If we're talking about tileset0 (the tileset for most overworld graphics including trees, rock, water, grass, etc), you have to be careful. You might have to end up trying to make your house fit within the palette scheme of one of those first few palettes instead of the other way around.
The easiest way to add in such a house would be through the 2nd tileset. Lots of tilesets put in the 2nd tileset don't use up all the palettes between 8 and 12, which means you would be free to use any of those unused palettes.
Hey, got a question about tiling. There is this blue house that I want to insert and it takes up all 16 colors. Which palette should I insert it at and what should I do for other tiles that might be affected by this pal change?