A good majority of the EU is trash. Lucas allowed it to happen so that fans could get new stories. They have even borrowed from EU from time to time, but there are some specific books where the Author has talked to Lucas or Pablo Hildalgo (curator of all things star wars) about specific events and they'd give them some information and the author would flesh it out. Lucasfilm took all those books you mentioned and said they are not canon. They said there are plenty of good stories in some of those books and that they may draw upon some of the good ones in the future to formally canonize them. For example, Darth Bane is known as the first Dark Lord of the Sith that instituted the rule of two. I believe the author did get some of this information from Lucas, but the story he wrote was mostly his own. Currently none of that story is canon. However, in the last season of Clone Wars they did make mention of Darth Bane and how he instituted the rule of two, so now Darth Bane as a character is canonized. There is a list of the new canon, its pretty sure but new books are coming out all the time.
https://en.wikipedia.org/wiki/Star_Wars_canon - scroll to the bottom
Another thing on the lightsaber color. Can a lightsaber be more powerful? We have not seen a red lightsaber cut through another color lightsaber. So to say one is more powerful than another is silly to me. No matter the color, if you get hit by the blade the end result is the same.