Cool Chest (R) Dainty Chest (R) Cute Chest (R) Sinister Chest (R) Hard Chest (B) Heavy Chest (B) Light Chest (B) Deluxe Chest (Y) Glittery Chest (Y) Gorgeous Chest (Y) Shiny Chest (Y)
What can come in each one of the chests?
In the Generation IV games, treasure boxes can contain different kinds of items that range from common food items to rare trade items that can be swapped in the Croagunk Swap Shop. They have to be appraised first at Xatu Appraisal located at Treasure Town before one can obtain the hidden item within the box. In certain dungeons, such as Zero Island North, Zero Island East, Zero Island West, and Zero Island South, there will be locked sections in which one must use a key to obtain the box. There may also be water blocking the box. These boxes will hold items such as legendary specialized items and Wonder Gummis. All boxes, with the exception of end-of-the-dungeon Deluxe Boxes and locked room boxes have random contents, though certain items will be unlocked as the game continues.
Directly ripped from here.