Chunk chunk1 = new Chunk("th");
Chunk chunk2 = new Chunk("i", bold);
Chunk chunk3 = new Chunk("s");

Paragraph p = new Paragraph();
p.add(chunk1); p.add(chunk2); p.add(chunk3)

public SpannableString colorizeText(String text) {
        SpannableString spannableColor = new SpannableString(text);
        int x = 1;
        for(char letter : text.toCharArray()){
            spannableColor.setSpan(new ForegroundColorSpan(returnCorrectColor(letter)), x-1, x, 0);
            x++;
        }
        return spannableColor;
    }

    private int returnCorrectColor(char letter) {
        String theLetter = Character.toString(letter);
        if (theLetter.contains("a")){
            return Color.BLUE;
        }
        else if(theLetter.contains("o")){
            return Color.GREEN;
        }
        return Color.RED;
    }