You can enter it with any non-hex characters that you want like such as 00:e0:b5:36:10:f5 or 00-e0-b5-36-10-f5.
This will NOT work if you leave out leading zeroes. For example some Cisco devices will give you 1:e0:5:6d:10:a6 where it should be 01:e0:05...
If this is the case, please put in the leading zeroes or your results will be inaccurate.
Note: This form manipulates the mac addr you entered and submits it to http://standards.ieee.org. I do not run the database of MAC addrs. This page merely provides a smoother interface to someone else's code.