The JBoss Log Manager you're using is quite old and I don't know much about it. I can give you information on the current release, 1.5.2.Final however.
JBoss Log Manager uses it's own configuration file format similar to log4j and it needs to be called logging.properties and in the class path or you can add a system property logging.configuration=file:path/to/file.properties
. Unfortunately at this point there is no real documentation on it, but I'll convert your log4j example to a JBoss Log Manager format.
# Additional loggers to configure (the root logger is always configured)
loggers=my.testpackage.MyClass,my
logger.level=INFO
logger.handlers=CONSOLE
logger.my.testpackage.MyClass.level=WARN
logger.my.level=WARN
handler.CONSOLE=org.jboss.logmanager.handlers.ConsoleHandler
handler.CONSOLE.level=INFO
handler.CONSOLE.formatter=COLOR-PATTERN
handler.CONSOLE.properties=autoFlush,target,enabled
handler.CONSOLE.autoFlush=true
handler.CONSOLE.target=SYSTEM_OUT
handler.CONSOLE.enabled=true
formatter.COLOR-PATTERN=org.jboss.logmanager.formatters.PatternFormatter
formatter.COLOR-PATTERN.properties=pattern
formatter.COLOR-PATTERN.pattern=%K{level}%d{HH\:mm\:ss,SSS} %-5p [%t] %c: %s%E%n