Backpacks are a form of storage which can be carried around. The regular backpack has 27 slots and the larger one has 54 slots. They can be dyed, but only during the initial crafting. To craft a backpack, place leather in a circle in a crafting bench. If you wish for it to be colored, add any color of dye in the middle of the circle of leather. If you do not add a color, it will be brown be default. If you want to color it to know which backpack is which is you have more then 1, consider renaming it as well. A larger version of the backpack is the Big backpack.