function main() {
    onOpen()
}

function onOpen() {
    var doc = DocumentApp.getActiveDocument()
        var body = doc.getBody()
        var text = body.editAsText()
        var colors = {
            "Person 1: " : "#000000",
            "Person 2: " : "#000000"
        }
    for (var person in colors) {
        var textRangesArray = findAll(person, text)
            for (var i = 0; i < textRangesArray.length; i++) {
                textRangesArray[i].getElement().setForegroundColor(textRangesArray[i].getStartOffset(), textRangesArray[i].getEndOffsetInclusive(), colors[person])
                    textRangesArray[i].getElement().setBold(textRangesArray[i].getStartOffset(), textRangesArray[i].getEndOffsetInclusive(), true)
            }
    }
}

function findAll(search, text) {
    var instances = []
        var foundElement = text.findText(search)
        while (foundElement !== null) {
            instances.push(foundElement)
                foundElement = text.findText(search, foundElement)
        }
    return instances
}