For making something be bold, it gets toggled on/off using $chr(2) the same way that html uses <b> and <b/> toggles. It doesn't matter whether you put the bold before or after the color code. So the formatting line looks more like

msg $active $chr(2) $+ $chr(3) $+ 52[ $+ $chr(2) $+ $chr(3) $+ 96 $+ $1- $+ $chr(2) $+ $chr(3) $+ 52] $+ $chr(2)

Note that the trailing chr2 isn't needed since it's already at the end of the line.
Also note that if you change the 96 to a single digit number like 3, you should make it be 03 so that if the message begins with a number, it wouldn't grab the 1st digit of the display as if it's part of the color code.