To complement the colors #fa3d59 (vibrant pinkish-red) and #fffcfb (soft off-white) with something unusual yet harmonious, I suggest adding #9b5dca , a muted lavender. This color introduces a unique twist while maintaining a soft elegance that pairs beautifully with the existing colors.

Here is the new color palette in JSON format:

json
{
  "palette_name": "Whimsical Elegance",
  "colors": [
    {
      "name": "Vibrant Pinkish-Red",
      "hex_code": "
                            
                            #fa3d59
                        "
    },
    {
      "name": "Soft Off-White",
      "hex_code": "
                            
                            #fffcfb
                        "
    },
    {
      "name": "Muted Lavender",
      "hex_code": "
                            
                            #9b5dca
                        "
    }
  ]
}

This palette combines the boldness of vibrant pinkish-red, the softness of off-white, and the unexpected charm of muted lavender, creating a whimsical and elegant color scheme. Would you like to see more unusual combinations or perhaps explore a different theme?