Set Todoist label colors from cosine similarity between a color description and tasks with the label. See https://ithoughthecamewithyou.com/post/set-todoist-label-colors-automatically-using-openai-embeddings

Code.gs

const TodoistApiToken = '';
const OpenAIApiKey = ''
const OpenAIResponseModel = 'gpt-5.4';
const OpenAIEmbeddingModel = 'text-embedding-3-small';

const TodoistColors = [
    {"id": 30, "name": "berry_red",   "hex": "#B8255F"},
    {"id": 31, "name": "red",         "hex": "#DC4C3E"},
    {"id": 32, "name": "orange",      "hex": "#C77100"},
    {"id": 33, "name": "yellow",      "hex": "#B29104"},
    {"id": 34, "name": "olive_green", "hex": "#949C31"},
    {"id": 35, "name": "lime_green",  "hex": "#65A33A"},
    {"id": 36, "name": "green",       "hex": "#369307"},
    {"id": 37, "name": "mint_green",  "hex": "#42A393"},
    {"id": 38, "name": "teal",        "hex": "#148FAD"},
    {"id": 39, "name": "sky_blue",    "hex": "#319DC0"},
    {"id": 40, "name": "light_blue",  "hex": "#6988A4"},
    {"id": 41, "name": "blue",        "hex": "#4180FF"},
    {"id": 42, "name": "grape",       "hex": "#692EC2"},
    {"id": 43, "name": "violet",      "hex": "#CA3FEE"},
    {"id": 44, "name": "lavender",    "hex": "#A4698C"},
    {"id": 45, "name": "magenta",     "hex": "#E05095"},
    {"id": 46, "name": "salmon",      "hex": "#C9766F"},
    {"id": 47, "name": "charcoal",    "hex": "#808080"},
    {"id": 48, "name": "grey",        "hex": "#999999"},
    {"id": 49, "name": "taupe",       "hex": "#8F7A69"}
]

function updateLabels() {
  const colorEmbeddings = loadEmbeddings(false);

  const labels = getLabels();

  for(const label of labels.results) {
    
    let labelText = `${label.name}\n`;
    
    const tasks = getTasks(label.name);
    
    for(const task of tasks.results) {
      labelText = labelText + `- ${task.content}`;

      if (task.priority == 1) {
        labelText = labelText + ' (High Priority)';
      } else if (task.priority == 4) {
        labelText = labelText + ' (Low Priority)';
      }

      labelText += '\n';
    }

    const labelEmbedding = generateEmbedding(labelText);
    let highestSimilarity = -1.0;
    let selectedColor = 47;
    for (const colorEmbedding of colorEmbeddings) {
      const similarity = cosineSimilarity(labelEmbedding, colorEmbedding.embedding);
      if (similarity > highestSimilarity) {
        highestSimilarity = similarity;
        selectedColor = colorEmbedding.id;
      }
    }
    updateLabelColor(label.id, selectedColor);
  }
}

function generateEmbedding(input) {
  const payload = {
    model: OpenAIEmbeddingModel,
    input: input
  };

  const options = {
      method: 'post',
      contentType: 'application/json',
      headers: {
        'Authorization': 'Bearer ' + OpenAIApiKey
      },
      payload: JSON.stringify(payload)
    };

  const response = UrlFetchApp.fetch('https://api.openai.com/v1/embeddings', options);
  const result = JSON.parse(response.getContentText());

  return result.data[0].embedding;
}

function forceEmbeddinbgs() {
  loadEmbeddings(true);
}

function loadEmbeddings(force) {
  const embeddings = [];
  const props = PropertiesService.getUserProperties();
  for (const color of TodoistColors) {
    var saved = props.getProperty(color.name);
    if (!saved || force) {
      saved = JSON.stringify(embeddingForColor(color.name, color.hex));
      props.setProperty(color.name, saved);
    }
    embeddings.push({'id': color.id, 'embedding': JSON.parse(saved)});
  }
  return embeddings;
}

function embeddingForColor(name, hex) {
  const messages = [];

  messages.push({
    role: 'developer',
    content: `You provide a paragraph descibing a color (the user will send you the name of the color and a specific hex color value).
  
  The paragraph includes what the color might signify to a person in the United States in terms of emotions, activities, common uses and associations.
  
  Describe the types of tasks on a to do list that might be associated with this color`
  });

  messages.push({
    role: 'user',
    content: 'Color Name: ' + name + ', Hex: ' + hex
  });

  const payload = {
    model: OpenAIResponseModel,
    messages: messages
  };

  const options = {
      method: 'post',
      contentType: 'application/json',
      headers: {
        'Authorization': 'Bearer ' + OpenAIApiKey
      },
      payload: JSON.stringify(payload)
    };

  const response = UrlFetchApp.fetch('https://api.openai.com/v1/chat/completions', options);
  const result = JSON.parse(response.getContentText());
  const description = result.choices[0].message.content;

  Logger.log(`Embedding for ${name} is ${description}.`)

  return generateEmbedding(description);
}

function getLabels() {
  var response = UrlFetchApp.fetch('https://api.todoist.com/api/v1/labels?limit=200', {
    headers: {
      Authorization: 'Bearer ' + TodoistApiToken
    }
  });

  return JSON.parse(response.getContentText());
}

function updateLabelColor(labelId, colorId) {
  const payload = {
    color: colorId
  };

  const options = {
    method: 'post',
    contentType: 'application/json',
    headers: {
      'Authorization': 'Bearer ' + TodoistApiToken
    },
    payload: JSON.stringify(payload)
  };

  UrlFetchApp.fetch(`https://api.todoist.com/api/v1/labels/${labelId}`, options);
}

function getTasks(label) {
  var response = UrlFetchApp.fetch(`https://api.todoist.com/api/v1/tasks?limit=3&label=${encodeURIComponent(label)}`, {
    headers: {
      Authorization: 'Bearer ' + TodoistApiToken
    }
  });

  return JSON.parse(response.getContentText());
}

function cosineSimilarity(A, B) {
    let dotproduct = 0;
    let magnitudeA = 0;
    let magnitudeB = 0;

    for (let i = 0; i < A.length; i++) {
        dotproduct += A[i] * B[i];
        magnitudeA += A[i] * A[i];
        magnitudeB += B[i] * B[i];
    }

    magnitudeA = Math.sqrt(magnitudeA);
    magnitudeB = Math.sqrt(magnitudeB);

    if (magnitudeA === 0 || magnitudeB === 0) {
        return 0; // Cosine similarity is undefined for zero vectors, return 0
    }

    const similarity = dotproduct / (magnitudeA * magnitudeB);
    return similarity;
}