I am putting a crate motor in my 01 XJ and I live in las vegas its coming on summer since my radiator will be drained and nothing in the block would it hurt the motor at all if i run (red) CAT coolant in my system to help keep it cooler? i know you can not mix the red with green or it will gell up

 

No it would not hurt anything they have the same chemical properties. Both ethylene glycol based.
No it wouldn't help in running "cooler"
Only difference would be the amount of time between fluid exchanges... The CAT coolant is an extended life coolant which is generally a 5yr/100k mile coolant. Me personally (also a Vegas native and former technician that still works in a shop [ted wiens] ) wouldn't bother with the cat coolant unless I had a stockpile off it.
They now make all makes all models universal coolant now that can be mixed with ANY color coolant.
If I were you I'd look into fan &/or fan clutch upgrades!