使用android.text.Spannable

final SpannableStringBuilder str = new SpannableStringBuilder(text);
str.setSpan(
    new ForegroundColorSpan(Color.BLUE), 
    wordStart, 
    wordEnd, 
    SpannableStringBuilder.SPAN_EXCLUSIVE_EXCLUSIVE
);
myTextView.setText(str);

编辑:让所有Java"变成绿色

EDIT: To make all "Java" green

final Pattern p = Pattern.compile("Java");
final Matcher matcher = p.matcher(text);

final SpannableStringBuilder spannable = new SpannableStringBuilder(text);
final ForegroundColorSpan span = new ForegroundColorSpan(Color.GREEN);
while (matcher.find()) {
    spannable.setSpan(
        span, matcher.start(), matcher.end(), Spanned.SPAN_EXCLUSIVE_EXCLUSIVE
    );
}
myTextView.setText(spannable);