The font-size and color depend on the list elements value property or, if no value is set, the elements index.
The tags in the cloud can be rendered randomly or in different styles, like as list, sphere or explosion.
You can set the minimum and maximum font-size with the properties sizemin and sizemax. Different font-sizes mean different cloud sizes so there's also the possibility to set its height.
Like font-size, you can also set the minimum and maximum color using colormin and colormax. The value must be a hexadecimal value with a length of either 3 or 6.