Can I color certain words in Google Document using Google Apps Script?

I'm trying to highlight certain words in my Google Document. I know I can replace text using document.replace, but it only replaces string itself, not formatting. Is there a way to replace string with colored string using Google Apps Script?

The key is to being able to reference just the words you want to color.

My solution is to:

Get the text of the paragraph that contains the words you wish to color, remove the original paragraph, then add each part of the text back. As you add each part back the appendText returns a reference to just the text added, you then can specify its color with setForegroundColor():

function highlightText() {
  var doc = DocumentApp.openById('<your document id>');
  var textToHighlight = 'dusty death';
  var textLength = textToHighlight.length;
  var paras = doc.getParagraphs();
  var paraText = '';
  var start;
  for (var i=0; i<paras.length; ++i) {
    paraText = paras[i].getText();
    start = paraText.indexOf(textToHighlight);
    if (start >= 0) {
      var preText = paraText.substr(0, start);
      var text = paraText.substr(start, textLength);
      var postText = paraText.substr(start + textLength, paraText.length);
      doc.removeChild(paras[i]);
      var newPara = doc.insertParagraph(i, preText);
      newPara.appendText(text).setForegroundColor('#FF0000');
      newPara.appendText(postText).setForegroundColor('#000000');
    }
  }
}