# PATCH Update a letter-part colour selection

Applies an RFC 7396 JSON Merge Patch to one letter-part colour selection: properties omitted from the body are unchanged, and `null` clears a nullable property (`name`, `description`, `optional_label`). Read-only and unknown fields are rejected — `letter_part` among them, because the path already carries it and a part cannot be renamed. An empty object `{}` is a valid no-op. The lightbox text and border rules apply here exactly as they do on the create. Requires `customisers:write`. An `Idempotency-Key` is optional here: sending one makes the update safe to retry. The update clears the customiser's cached storefront configuration and runs the advisory language sync, and never regenerates Shopify products, product images, or the product cache.

- Source URL: https://www.signcustomiser.com/help/api/v3-patch-update-a-letter-part-colour-selection/
- Markdown URL: https://www.signcustomiser.com/help/api/v3-patch-update-a-letter-part-colour-selection.md
- Group: Customiser letter parts
- Method: PATCH
- Path: /api/v3/customisers/{customiser_id}/letter-types/{letter_type_id}/letter-parts/{letter_part}
- Auth: Bearer token
- Required scopes: `customisers:write`

## Path parameters

- customiser_id (string, required): The customiser id. Example: 1
- letter_type_id (string, required): The letter type id. Example: 7
- letter_part (string, required): The letter part. Example: face

## Body parameters

- name (string, optional): No description provided.
- optional (boolean, optional): No description provided.
- optional_label (string, optional): No description provided.
- optional_default_none (boolean, optional): No description provided.
- lightsource (boolean, optional): No description provided.
- custom_image (boolean, optional): No description provided.
- show_default_upload_image (boolean, optional): No description provided.
- show_in_text_editor (boolean, optional): No description provided.
- text_enabled (boolean, optional): No description provided.

## Request body example

```json
{
  "name": "Face colour",
  "optional": true,
  "optional_label": "No face colour",
  "optional_default_none": false,
  "lightsource": true,
  "custom_image": false,
  "show_default_upload_image": true,
  "show_in_text_editor": true,
  "text_enabled": false
}
```

## cURL example

```bash
curl https://web.signcustomiser.com/api/v3/customisers/1/letter-types/7/letter-parts/face \
  --request PATCH \
  --header 'Accept: application/json' \
  --header 'Authorization: Bearer YOUR_API_TOKEN' \
  --header 'Content-Type: application/json' \
  --data '{
  "name": "Face colour",
  "optional": true,
  "optional_label": "No face colour",
  "optional_default_none": false,
  "lightsource": true,
  "custom_image": false,
  "show_default_upload_image": true,
  "show_in_text_editor": true,
  "text_enabled": false
}'
```

## Response examples

### 200 PATCH 200 example 1

```json
{
  "data": {
    "object": "letter_part_colour_selection",
    "customiser_id": 42,
    "letter_type_id": 7,
    "letter_part": "face",
    "name": "Face colour",
    "description": null,
    "optional": true,
    "optional_label": "No face colour",
    "optional_default_none": false,
    "lightsource": true,
    "custom_image": false,
    "show_default_upload_image": true,
    "show_in_text_editor": true,
    "text_enabled": false,
    "default_upload_image_url": null,
    "created_at": "2026-08-13T00:00:00Z",
    "updated_at": "2026-08-13T00:05:00Z"
  },
  "links": {
    "self": "https://web.signcustomiser.com/api/v3/customisers/42/letter-types/7/letter-parts/face",
    "documentation": "https://www.signcustomiser.com/help/api/"
  },
  "meta": {
    "api_version": "v3",
    "request_id": "req_01jz9x2k7c8f3m5n6p7q8r9s0t"
  }
}
```

### 400 Malformed JSON body

```json
{
  "type": "https://www.signcustomiser.com/help/api/problems/malformed_json",
  "title": "Malformed JSON",
  "status": 400,
  "code": "malformed_json",
  "detail": "The request body is not valid JSON: Syntax error.",
  "request_id": "req_01jz9x2k7c8f3m5n6p7q8r9s0t"
}
```

### 401 Missing API key

```json
{
  "type": "https://www.signcustomiser.com/help/api/problems/missing_api_key",
  "title": "Missing API key",
  "status": 401,
  "code": "missing_api_key",
  "detail": "Provide a store API key as a bearer token.",
  "request_id": "req_01jz9x2k7c8f3m5n6p7q8r9s0t"
}
```

### 403 Insufficient scope

```json
{
  "type": "https://www.signcustomiser.com/help/api/problems/insufficient_scope",
  "title": "Insufficient scope",
  "status": 403,
  "code": "insufficient_scope",
  "detail": "This operation requires the customisers:write scope.",
  "required_scopes": [
    "customisers:write"
  ],
  "granted_scopes": [
    "customisers:read"
  ],
  "request_id": "req_01jz9x2k7c8f3m5n6p7q8r9s0t"
}
```

### 404 Unknown letter part

```json
{
  "type": "https://www.signcustomiser.com/help/api/problems/resource_not_found",
  "title": "Resource not found",
  "status": 404,
  "code": "resource_not_found",
  "detail": "The requested resource does not exist or does not belong to the authenticated store.",
  "request_id": "req_01jz9x2k7c8f3m5n6p7q8r9s0t"
}
```

### 409 Idempotency conflict

```json
{
  "type": "https://www.signcustomiser.com/help/api/problems/idempotency_key_conflict",
  "title": "Idempotency key conflict",
  "status": 409,
  "code": "idempotency_key_conflict",
  "detail": "This Idempotency-Key was already used for a different request body on this operation.",
  "request_id": "req_01jz9x2k7c8f3m5n6p7q8r9s0t"
}
```

### 413 Request body too large

```json
{
  "type": "https://www.signcustomiser.com/help/api/problems/request_too_large",
  "title": "Request too large",
  "status": 413,
  "code": "request_too_large",
  "detail": "The request body must not exceed 2 MiB.",
  "request_id": "req_01jz9x2k7c8f3m5n6p7q8r9s0t"
}
```

### 422 Customer text not supported

```json
{
  "type": "https://www.signcustomiser.com/help/api/problems/customer_text_not_supported",
  "title": "Customer text not supported",
  "status": 422,
  "code": "customer_text_not_supported",
  "detail": "Customer text renders on the front face of a rectangle or cylinder lightbox only.",
  "errors": [
    {
      "pointer": "/text_enabled",
      "code": "customer_text_not_supported",
      "detail": "This letter part cannot carry customer text."
    }
  ],
  "request_id": "req_01jz9x2k7c8f3m5n6p7q8r9s0t"
}
```

### 429 Option write budget exhausted

```json
{
  "type": "https://www.signcustomiser.com/help/api/problems/rate_limited",
  "title": "Too many requests",
  "status": 429,
  "code": "rate_limited",
  "detail": "You have exceeded the request limit for this API key.",
  "retry_after": 37,
  "request_id": "req_01jz9x2k7c8f3m5n6p7q8r9s0t"
}
```