Here is a dark theme color palette centered around gray:

{
  "palette_name": "Dark Gray Theme",
  "colors": [
    {
      "name": "Charcoal",
      "hex_code": "
                            
                            #333333
                        "
    },
    {
      "name": "Slate Gray",
      "hex_code": "
                            
                            #708090
                        "
    },
    {
      "name": "Dim Gray",
      "hex_code": "
                            
                            #696969
                        "
    },
    {
      "name": "Gunmetal",
      "hex_code": "
                            
                            #2a3439
                        "
    },
    {
      "name": "Ash Gray",
      "hex_code": "
                            
                            #B2B2B2
                        "
    }
  ]
}

This palette features a range of gray tones suitable for a dark theme, providing depth and contrast while maintaining a sleek aesthetic.

What other elements would you like to incorporate into your design?