Not really. A hash is just a number (or perhaps more accurately, a string of bits). Hexadecimal is a way of representing numbers in base-16.  A hash can be represented in many ways because it is just a string of bits. For example, a Bitcoin address is a hash (plus some other things), but you normally see it as base-58, and not hexadecimal. Base-64 is also a common way to represent hashes.