Here is a color palette based on your request for a dark blue theme, avoiding purple colors:

json
{
  "palette_name": "Dark Blue Web Application",
  "colors": [
    {
      "name": "Midnight Blue",
      "hex_code": "
          
          #001f3f
       "
    },
    {
      "name": "Dark Slate Blue",
      "hex_code": "
          
          #003366
       "
    },
    {
      "name": "Steel Blue",
      "hex_code": "
          
          #4682B4
       "
    },
    {
      "name": "Light Blue",
      "hex_code": "
          
          #ADD8E6
       "
    },
    {
      "name": "Cadet Blue",
      "hex_code": "
          
          #5F9EA0
       "
    }
  ]
}

This palette features a range of blues that create a cohesive and professional look for a web application. Would you like assistance with anything else, such as suggestions for font styles or UI elements that complement this palette?