I personally use
/console SET chatClassColorOverride “0”
This shows classes in chat with different colors.
Rogue = Yellow
Mage = Blue
Hunter = Green
Warlock = Purple
Shaman & Paladin = Pink
Priest = White
If you wanna go the extra step, in retail you can change how many fireballs, or frostbolts flies down from blizzard or rain of fire. It would be /console spelleffectlevel 1-999999 (I recommend starting at 1000)
In order to do this in Vanilla you have to go to the classic folder , into WTF folder, open “config” and enter as following: SET spelleffectlevel “250”
Save and login to WoW Classic again, and use one of the two. (Might work on more spells aswell.