How can I achieve colored specular effect like UDK ?
What I want is an object taking a white light and reflecting it as different color(green in example)
http://s27.postimg.org/6vroyf835/image.png
I guess the specular system in Unreal Engine 4 works different now.
The current shading system(PBR) doesnt allow colored speculars as in UDK. You can see that effect only in metallic materials(metallic value 1 or at least above 0.5 to see it better) and it will tint the reflection with the diffuse(base) color. Also specular input wont change anything with metallic materials so you can leave it empty.
Thanks for the info.
So is it not any way possible to achieve same effect like first picture ?
You can fake it i suppose by getting the light vector via blueprints(LightVector isnt available in the material anymore either so you’ll have to get it via blueprints), and you also have the source code but i dont know how it can be achieved with coding.
You can also get a similar effect (you will have to play with the values a bit as it is not perfect) but click on the material node so it is highlighted, and then in details panel change the “Shading Model” to “Subsurface”, and then plug your green node into the “Subsurface Color” slot. It gives you a similar effect, not exact, but might be a good starting point to see what you can come up with! 
http://s28.postimg.org/j94mg9hkr/Capture.png
I tryed some options and one seems to give the similar effect.
Using power output as alpha gives softer transitions and costing 2 more instructions.