Hi ! Here the color changing foods I found for the 20th Anniversary mix :
Red : Watermelon juice (Suika jūsu) 130₲ (Snack at Restaurant)
Tomato ramen (Tomato rāmen) 110₲ (Meal at Restaurant)
Minestrone (Minesutorōne) 160₲ (Meal at Restaurant)
Peach (Momo) 100₲ (Snack at Makkakka Town)...