How to provide background color for the label fields when sending document for signature?

curl -X 'POST' \
  'https://api.boldsign.com/v1/document/send' \
  -H 'accept: application/json' \
  -H 'X-API-KEY: {Your API Key}' \
  -H 'Content-Type: multipart/form-data' \
  -F 'Signers={
  "name": "Richard",
  "emailAddress": "richard@boldsign.dev",
  "formFields": [
    {
      "id": "sign",
      "fieldType": "Signature",
      "pageNumber": 1,
      "bounds": {
        "x": 100,
        "y": 100,
        "width": 200,
        "height": 20
      },
      "isRequired": true
    },
{
      "id": "label1",
      "fieldType": "Label",
      "pageNumber": 1,
      "bounds": {
        "x": 200,
        "y": 200,
        "width": 200,
        "height": 20
      },
      "isRequired": true,
       "value": "Sample",
      "backgroundHexColor": "#00FFFF"
    }
  ],
  "locale": "EN"
}' \
  -F 'Files=@{Your File Path}' \
  -F 'Title=Sample document' \

using BoldSign.Api;
using BoldSign.Model;

var apiClient = new ApiClient("https://api.boldsign.com", "Your API Key");
var documentClient = new DocumentClient(apiClient);

var documentFilePath = new DocumentFilePath
{
   ContentType = "application/pdf",
   FilePath = "{Your file path}",
};

var filesToUpload = new List<IDocumentFile>
{
    documentFilePath,
};

var signatureField = new FormField(
   id: "sign",
   isRequired: true,
   type:FieldType.Signature,
   pageNumber: 1,
   bounds: new Rectangle(x: 100, y: 100, width: 100, height: 50));

var labelField = new FormField(
   id: "label",
   isRequired: true,
   value:"Sample",
   type: FieldType.Label,
   pageNumber: 1,
   bounds: new Rectangle(x: 200, y: 400, width: 100, height: 50));   

labelField.BackgroundHexColor = "#FF00FF";  

var formFieldCollections = new List<FormField>()
{
    signatureField,
    labelField
};

var signer = new DocumentSigner(
  signerName: "Richard",
  signerType: SignerType.Signer,
  signerEmail: "richard@boldsign.dev",
  formFields: formFieldCollections,
  locale: Locales.EN);

var documentSigners = new List<DocumentSigner>()
{
    signer
};

var sendForSign = new SendForSign()
{
   Message = "please sign this",
   Title = "Agreement",
   Signers = documentSigners,
   Files = filesToUpload,

};
var documentCreated = documentClient.SendDocument(sendForSign);
Console.WriteLine(documentCreated.DocumentId);

import requests
import json

url = "https://api.boldsign.com/v1/document/send"

signer_data = {
    "name": "Richard",
    "emailAddress": "richard@boldsign.dev",
    "signerType": "Signer",
    "formFields": [
        {
            "id": "Sign1",
            "name": "Sign1",
            "fieldType": "Signature",
            "pageNumber": 1,
            "bounds": {
                "x": 50,
                "y": 50,
                "width": 200,
                "height": 25
            },
            "isRequired": True
        },
        {
            "id": "Label1",
            "name": "Label1",
            "fieldType": "Label",
            "value":"Sample",
            "pageNumber": 1,
            "bounds": {
                "x": 150,
                "y": 250,
                "width": 200,
                "height": 25
            },
            "backgroundHexColor": "#00FFFF"
        }
    ],
    "locale": "EN"
}

payload = {
    'Message': 'Please sign this.',
    'Signers': json.dumps(signer_data),
    'Title': 'Agreement',
}

files=[
  ('Files',('file',open('{Your file path}','rb'),'application/pdf'))
]

headers = {
  'accept': 'application/json',
  'X-API-KEY': '{Your API Key}'
}

response = requests.request("POST", url, headers=headers, data=payload, files=files)

print(response.text)

const axios = require('axios');
const fs = require('fs');
const FormData = require('form-data');

const url = "https://api.boldsign.com/v1/document/send";

const signerData = {
    name: "Richard",
    emailAddress: "richard@boldsign.dev",
    signerType: "Signer",
    formFields: [
        {
            id: "Sign1",
            name: "Sign1",
            fieldType: "Signature",
            pageNumber: 1,
            bounds: {
                x: 50,
                y: 50,
                width: 200,
                height: 25
            },
            isRequired: true
        },
        {
            id: "Label1",
            name: "Label1",
            fieldType: "Label",
            value:"Sample",
            pageNumber: 1,
            bounds: {
                x: 150,
                y: 250,
                width: 200,
                height: 25
            },
            isRequired: true,
            backgroundHexColor: "#00FFFF"
        }
    ],
    locale: "EN"
};

const formData = new FormData();
formData.append('Message', 'Please sign this.');
formData.append('Signers', JSON.stringify(signerData));
formData.append('Title', 'Agreement');
formData.append('Files', fs.createReadStream('{Your file path}'), 'application/pdf');

const headers = {
  'accept': 'application/json',
  'X-API-KEY': '{Your API Key}',
  ...formData.getHeaders()
};

axios.post(url, formData, { headers })
    .then(response => {
        console.log(response.data);
    })
    .catch(error => {
        console.error(error);
    });