What are the blue edges and how to get rid of them
Blue edges are typically open edges, which are not connected to another edge. However, in your image, it doesn't look like that scenario. My guess is that you have the sectioning mode turned on. I noticed that when loading the sectioning window, we will leave the cutting plane visible even after closing the window.
Does that sound familiar? Did you try using the sectioning window. I can make a note to make sure we turn then off after closing the window.
In the image you attached, I don't see any blue edges. Could you point them out to me please? They do seem to be gone but I may be missing them.
Please let me know.
By the way, I'm sure you already know this but I just wanted to confirm that the purple/magenta edges are creases so those appear as expected.