I have came up with this post but it is for the deprecated Google Maps API
http://tech.truliablog.com/2012/02/23/custom-map-markers-for-android-google-maps/
by referring to Google's sample code
IconGenerator iconFactory = new IconGenerator(this);
iconFactory.setColor(Color.CYAN);
addIcon(mMap, iconFactory, "Custom color", new LatLng(-33.9360, 151.2070));
addIcon() Method here:
private void addIcon(GoogleMap googleMap, IconGenerator iconFactory, CharSequence text, LatLng position) {
MarkerOptions markerOptions = new MarkerOptions().
icon(BitmapDescriptorFactory.fromBitmap(iconFactory.makeIcon(text))).
position(position).
anchor(iconFactory.getAnchorU(), iconFactory.getAnchorV());
googleMap.addMarker(markerOptions);
}