Question is this old physical sunder works with warlock too?

Yes but its not really worth it

The only upside to physical sunder is that unlike the other charms it allows your amplify damage / sigil lethargy to apply their full -%DR instead of the 1/5 value they normally get, otherwise all sunder would do is -5% DR on the 100% DR monsters. There are extremely few monsters that can be 110%+ DR because they almost all cap out at 50% DR or have 100% native DR and either way will have 100% DR with stone skin, only a handful like blunderbores in frigid will be 125% DR with stone skin. So with a ~35% sigil and 100% amp on your demon, a non-bone break warlock will turn a physical immune monster into 73% DR, while a bone break will make it -40% DR
but aside from a physical immune herald of terror, nothing in the game has the HP to survive echoing strikes even at 73% DR post-amp/sigil
meanwhile you're gimping yourself by having -10% DR to yourself against what is by far the most common damage type in the game

Also i seen in game when they throw theur echoing strike some of them are green purple like mine.. how is that?

Depends what the warlock eat. Sometimes it’s green. Sometimes it’s purple. Sometimes it’s brown. Ya know?

Depends on what hex you use. Check the right side of the eldritch tree.

yup already figure it out tnx