最简单的方法是

setNumberPickerTextColor(mNumberPicker);

public void setNumberPickerTextColor(NumberPicker numberPicker){
    int color=Color.parseColor("#333333");

    final int count = numberPicker.getChildCount();
    for(int i = 0; i < count; i++){
        View child = numberPicker.getChildAt(i);
        if(child instanceof EditText){
            try{
                Field selectorWheelPaintField = numberPicker.getClass().getDeclaredField("mSelectorWheelPaint");
                selectorWheelPaintField.setAccessible(true);
                ((Paint)selectorWheelPaintField.get(numberPicker)).setColor(color);
                ((EditText)child).setTextColor(color);
                numberPicker.invalidate();
            }
            catch(NoSuchFieldException e){
                Log.e("setNumberPickerColor1", ""+e);
            }
            catch(IllegalAccessException e){
                Log.e("setNumberPickerColor2", ""+e);
            }
            catch(IllegalArgumentException e){
                Log.e("setNumberPickerColor3", ""+e);
            }
        }
    }
}