I can personally say!! Give it 3 months. I got my suggie in April, he was a dark cinnamon brown. I IMMEDIATELY put him on LGRS suggie soup with 1 tbsp each of protein (boiled chicken, boiled egg, or mealies) and fruits and veggies. I just noticed last week he is half gray now and losing that dark brown stain! I'll give mine another month before he is COMPLETELY gray. So give it 3 months before physically seeing change
Also, stay away from pellets. They are not all that great for suggie's health and they are the cause of that brown color. Feed them as much fresh food as possible.