curl --request PATCH \
  --url https://{your-subdomain}.neetoform.com/api/external/v2/themes/{id} \
  --header 'Content-Type: application/json' \
  --header 'X-Api-Key: <x-api-key>' \
  --data '
{
  "theme": {
    "name": "Brand",
    "properties": {
      "eui_font_family": "Inter, sans-serif",
      "question_color": "#123456",
      "background_color": "#ffffff",
      "button_text_color": "#ffffff",
      "button_background_color": "#1a2b3c",
      "button_border_radius": "10"
    }
  }
}
'

const options = {
  method: 'PATCH',
  headers: {'X-Api-Key': '<x-api-key>', 'Content-Type': 'application/json'},
  body: JSON.stringify({
    theme: {
      name: 'Brand',
      properties: {
        eui_font_family: 'Inter, sans-serif',
        question_color: '#123456',
        background_color: '#ffffff',
        button_text_color: '#ffffff',
        button_background_color: '#1a2b3c',
        button_border_radius: '10'
      }
    }
  })
};

fetch('https://{your-subdomain}.neetoform.com/api/external/v2/themes/{id}', options)
  .then(res => res.json())
  .then(res => console.log(res))
  .catch(err => console.error(err));

import requests

url = "https://{your-subdomain}.neetoform.com/api/external/v2/themes/{id}"

payload = { "theme": {
        "name": "Brand",
        "properties": {
            "eui_font_family": "Inter, sans-serif",
            "question_color": "#123456",
            "background_color": "#ffffff",
            "button_text_color": "#ffffff",
            "button_background_color": "#1a2b3c",
            "button_border_radius": "10"
        }
    } }
headers = {
    "X-Api-Key": "<x-api-key>",
    "Content-Type": "application/json"
}

response = requests.patch(url, json=payload, headers=headers)

print(response.text)

{
  "theme": {
    "id": "3b0d5c1e-2f7a-4c4e-9d1b-6a8f2e7c9b10",
    "name": "Brand",
    "is_system_theme": false,
    "properties": [
      {
        "key": "background_color",
        "kind": "color",
        "value": "#ffffff"
      }
    ],
    "has_background_image": false
  }
}

{
  "error": "param is missing or the value is empty: theme"
}

{
  "error": "NeetoThemesEngine::Theme does not exist."
}

{
  "error": "These theme properties cannot be set here: custom_css. Editable properties: eui_font_family, question_color, background_color, button_text_color, button_background_color, button_border_radius, welcome_text_alignment, questions_text_alignment, thank_you_text_alignment."
}