You can do it with SCT, although it'll squeal when _any_ Hunter's trap is resisted according to that message (i.e. it's not "Your freezing trap", it's "Freezing Trap III's Freezing Trap is".)
Open up your SCT folder and go to the SCT_Event_Config.lua and open it up. Scroll down a bit and you'll see something like...
[1] = {name="Clearcast!", search="You gain Clearcast", r=256/256, g=256/256, b=0/256, class={"Mage","Shaman","Druid"}},
And more events after that. Go to the bottom of the list (13 is the last one on mine, adjust the number as needed) and copy and paste this in.
[14] = {name="Trap Resist!", search="Freezing Trap III's Freezing Trap Effect was resisted(.*)", r=128/256, g=128/256, b=256/256, frame=SCT.MSG},
You can adjust the color of the message by editing the RGB values. This one should show up as Green iirc.
This depends on the combat text provided being accurate; if it's not, it'll have to be modified, but that should work.