Red lightning

I noticed in DOTA 5.54, the hero Razor had a normal attack that was red lightning(Finger of Pain?).

How can I make a hero with red lightning as their normal attack?

Gotta give him the chimera's Lightning Attack ability. Change the ligth effect for that skill to get teh finger of death art.

how do I change the lightning effect of it if it is his attack?

Object Editor> Abilities> Lightning Attack> Lightning Effect> Finger of Death

If you do not have this field in your editor, you're probably using RoC and well, to do this is RoC involves importing a .slk file and has more steps than I can recall.