How to search "error." pattern with LOG

I am trying to monitor a log file in order to be alerted when the
string
"error." appears.

For instance :

error.grammar
error.noressource

... should send an alert

but "error " (with a space after) should not.

The '.' in your expression matches 'any character', not the characteter
'.'
You need to 'escape' (precede it with a '\' it to force it to mean the
actual character '.'

Try using
	LOG     /tmp/log "%error\." COLOR=yellow