Here is a color palette based on your request for all 12 colors of the rainbow, with lighter and darker shades for each color:

json
{
  "palette_name": "Gentle Rainbow",
  "colors": [
    {
      "name": "Light Red",
      "hex_code": "
                            
                            #FF7F7F
                        "
    },
    {
      "name": "Red",
      "hex_code": "
                            
                            #FF4C4C
                        "
    },
    {
      "name": "Dark Red",
      "hex_code": "
                            
                            #BF0000
                        "
    },
    {
      "name": "Light Orange",
      "hex_code": "
                            
                            #FFA07A
                        "
    },
    {
      "name": "Orange",
      "hex_code": "
                            
                            #FF8C00
                        "
    },
    {
      "name": "Dark Orange",
      "hex_code": "
                            
                            #BF5C00
                        "
    },
    {
      "name": "Light Yellow",
      "hex_code": "
                            
                            #FFFFB3
                        "
    },
    {
      "name": "Yellow",
      "hex_code": "
                            
                            #FFFF00
                        "
    },
    {
      "name": "Dark Yellow",
      "hex_code": "
                            
                            #BFBF00
                        "
    },
    {
      "name": "Light Green",
      "hex_code": "
                            
                            #B2FF99
                        "
    },
    {
      "name": "Green",
      "hex_code": "
                            
                            #4CFF00
                        "
    },
    {
      "name": "Dark Green",
      "hex_code": "
                            
                            #008000
                        "
    },
    {
      "name": "Light Blue",
      "hex_code": "
                            
                            #99CCFF
                        "
    },
    {
      "name": "Blue",
      "hex_code": "
                            
                            #007FFF
                        "
    },
    {
      "name": "Dark Blue",
      "hex_code": "
                            
                            #003D99
                        "
    },
    {
      "name": "Light Indigo",
      "hex_code": "
                            
                            #A8A0FF
                        "
    },
    {
      "name": "Indigo",
      "hex_code": "
                            
                            #4B0082
                        "
    },
    {
      "name": "Dark Indigo",
      "hex_code": "
                            
                            #2E005D
                        "
    },
    {
      "name": "Light Violet",
      "hex_code": "
                            
                            #D1A6FF
                        "
    },
    {
      "name": "Violet",
      "hex_code": "
                            
                            #8A2BE2
                        "
    },
    {
      "name": "Dark Violet",
      "hex_code": "
                            
                            #5B2E91
                        "
    }
  ]
}

This palette features a range of shades for each of the 12 colors of the rainbow, transitioning from light to dark tones to create a gentle and harmonious visual experience.

Would you like to explore any specific colors further or seek additional palettes?