Here is a color palette designed for Excel with 24 colors, ensuring that black text remains readable against each background color:

json
{
  "palette_name": "Excel Readable Colors",
  "colors": [
    {"name": "Light Blue", "hex_code": "
          
          #ADD8E6
       "},
    {"name": "Light Coral", "hex_code": "
          
          #F08080
       "},
    {"name": "Light Goldenrod Yellow", "hex_code": "
          
          #FAFAD2
       "},
    {"name": "Light Green", "hex_code": "
          
          #90EE90
       "},
    {"name": "Light Sky Blue", "hex_code": "
          
          #87CEFA
       "},
    {"name": "Light Pink", "hex_code": "
          
          #FFB6C1
       "},
    {"name": "Light Salmon", "hex_code": "
          
          #FFA07A
       "},
    {"name": "Peach Puff", "hex_code": "
          
          #FFDAB9
       "},
    {"name": "Misty Rose", "hex_code": "
          
          #FFE4E1
       "},
    {"name": "Lavender", "hex_code": "
          
          #E6E6FA
       "},
    {"name": "Honeydew", "hex_code": "
          
          #F0FFF0
       "},
    {"name": "Mint Cream", "hex_code": "
          
          #F5FFFA
       "},
    {"name": "Light Yellow", "hex_code": "
          
          #FFFFE0
       "},
    {"name": "Light Sea Green", "hex_code": "
          
          #20B2AA
       "},
    {"name": "Powder Blue", "hex_code": "
          
          #B0E0E6
       "},
    {"name": "Thistle", "hex_code": "
          
          #D8BFD8
       "},
    {"name": "Pale Turquoise", "hex_code": "
          
          #AFEEEE
       "},
    {"name": "Peach", "hex_code": "
          
          #FFDAB9
       "},
    {"name": "Lemon Chiffon", "hex_code": "
          
          #FFFACD
       "},
    {"name": "Lavender Blush", "hex_code": "
          
          #FFF0F5
       "},
    {"name": "Light Slate Gray", "hex_code": "
          
          #778899
       "},
    {"name": "Light Steel Blue", "hex_code": "
          
          #B0C4DE
       "},
    {"name": "Pale Goldenrod", "hex_code": "
          
          #EEE8AA
       "},
    {"name": "Floral White", "hex_code": "
          
          #FFFAF0
       "},
    {"name": "Alice Blue", "hex_code": "
          
          #F0F8FF
       "}
  ]
}

This palette includes a variety of light colors that will ensure good contrast with black text, making the content easily readable.

Would you like to customize this palette further, or do you have any other queries related to color usage in Excel?