- To color it you need to feed the resulting value as alpha mask in to Lerp node. Or just make RGB vector by appending 2 float 0 to it (X-0-0).
- To fire it you need to drive a parameter by blueprint, like animation graph.
- To place an origin within player location you need to feed a vector of current player position as a parameter.
All those questions were answered here on Answerhub or Forums, there are even tutorial on YT on that matter.
You could also use PP sonar effect: https://forums.unrealengine.com/development-discussion/rendering/22363-radar-sonar-pulse-post-processing-material