What can I do when my potato slices do not turn golden brown? I heard this might be because of the sugar, is that true? 

This is a case of ‘it depends.’ As in, how are you trying to prepare the potatoes? Boiling the potatoes for instance, won’t caramelize as the surface sugars don’t adhere to the surface. Other methods (pan frying, roasting, hash brown, au gratin, etc.) are all preparation methods that the surface sugars are in contact with the heat source directly and normally turn a golden brown on these surfaces, causing the chemical reaction that creates the golden brown color as the potatoes cook.