Here is the color palette reordered from lightest to darkest:

json
{
  "palette_name": "Ordered Transition from Lightest to Darkest",
  "colors": [
    {
      "name": "Amethyst",
      "hex_code": "
                            
                            #9966CC
                        "
    },
    {
      "name": "Medium Purple",
      "hex_code": "
                            
                            #9370DB
                        "
    },
    {
      "name": "Purple Heart",
      "hex_code": "
                            
                            #9B59B6
                        "
    },
    {
      "name": "Royal Purple",
      "hex_code": "
                            
                            #7851A9
                        "
    },
    {
      "name": "Rebecca Purple",
      "hex_code": "
                            
                            #663399
                        "
    }
  ]
}

In this reordered palette, the colors transition from the lighter shade of Amethyst to the darker shade of Rebecca Purple.

Would you like to explore any further adjustments or other color themes?