[Aliassassin123456]

Metharon is right, it's a bug. (with entering a %s and using it on format, it will fuck the server)
There's a filter on message with OnPlayerText and OnPlayerCommandText, it removes % on input and also colors on input too!
But you can use the filter which is using on OnPlayerText and OnPlayerCommandText:

Code:

for(new i = 0, j = strlen(input); i < j; i++)
{
	if(input[i] == '%') input[i] = '#';
}

Also you must write a code to filter color embedding like {FFFFFF} (isn't a vulnerability but player mustn't be able to use embedded colors IMO)
Easy to write, I'll post it here soon.