The error I get is...
As of Arduino 1.0, the 'BYTE' keyword is no longer supported.
Please use Serial.write() instead.
so the compiler actually tells you what to use.
Also, reading the release notes http://arduino.cc/en/Main/ReleaseNotes
* The behavior of Serial.print() on a byte has been changed to align it
with the other numeric data types. In particular, it will now print
the digits of its argument as separate ASCII digits (e.g. '1', '2', '3')
rather than a single byte. The BYTE keyword has been removed. To send a
single byte of data, use Serial.write() (which is present in Arduino 0022