Yes, it is. If you got photoshop, just search on the file in the warcraft mpq with your lightning data, change the color in photoshop and implement it in your map. Bum! Yellow lightning.
Or you could trigger the whole spell and then change the color manually.
Untitled Trigger 003
Events
Unit - A unit Starts the effect of an ability
Conditions
(Ability being cast) Equal to 'YourChainLightning'
Actions
Lightning - Create a lightning effect Chain Lightning - Primary (Position of (Casting unit)) (Position of (Target unit of ability being cast))
Lightning - Change (Last created lightning effect) color to 1.00 85.00 0.00 1.00
Wait 0.50 seconds
Lightning - Destroy (Last created lightning effect)
this is really easy... you can change the color of lightning to any color you want it.. change the width, height, transperency, etc...
you need a file called lightningdata.slk, its an excel file
http://www.thehelper.net/forums/showthread.php?t=73998&highlight=shadow+burst
the spell is shadow burst, it is being used in that spell... the file is imported in the map... you can edit the values...
there was a small tutorial on that file... can't seem to find it... its on this site somewhere