Is it possible to change the text color in a string to multiple colors in Java?

A simple way to do it is to use HTML and set the text to the TextView programmatically.

String text = "This text is white. <font color=\"blue\">This text is blue.</font>";
textView.setText(Html.fromHtml(text), BufferType.SPANNABLE);

Yes, its possible. For this you need to use SpannableString and ForegroundColorSpan.

This should look something like this:

SpannableStringBuilder builder = new SpannableStringBuilder();

String red = "this is red";
SpannableString redSpannable= new SpannableString(red);
redSpannable.setSpan(new ForegroundColorSpan(Color.RED), 0, red.length(), 0);
builder.append(redSpannable);

String white = "this is white";
SpannableString whiteSpannable= new SpannableString(white);
whiteSpannable.setSpan(new ForegroundColorSpan(Color.WHITE), 0, white.length(), 0);
builder.append(whiteSpannable);

String blue = "this is blue";
SpannableString blueSpannable = new SpannableString(blue);
blueSpannable.setSpan(new ForegroundColorSpan(Color.BLUE), 0, blue.length(), 0);
builder.append(blueSpannable);

mTextView.setText(builder, BufferType.SPANNABLE);