I solved it programmatically using this code:
final Drawable upArrow = getResources().getDrawable(R.drawable.abc_ic_ab_back_mtrl_am_alpha);
upArrow.setColorFilter(Color.parseColor("#FFFFFF"), PorterDuff.Mode.SRC_ATOP);
getSupportActionBar().setHomeAsUpIndicator(upArrow);
Revision 1:
Starting from API 23 (Marshmallow) the drawable resource abc_ic_ab_back_mtrl_am_alpha
is changed to abc_ic_ab_back_material
.