Why are all these different colored lines showing up in Edit Mode? I was working on a project and went to edit a mesh when suddenly, all these multi colored lines appear (in a glitchy-looking way, like when you duplicate a mesh in the same position).



I did some googling, and it seems that the colors represent things like Crease, Bevel, Sharp, etc. But I can't figure out how to hide them from view, which is really annoying.

Hope someone can shed some light on this issue.
The white lines are most likely edges, that have been "marked as sharp". 

This happens quite often, when importing objects from other file formats.

Select your mesh, go into Edit Mode, hit A to select everything, then hit Ctrl+E and select "Clear Sharp" in the popup menu. 



There also might be double vertices in your mesh (hard to say from the image alone). 

To remove double vertices, select your mesh, go into edit mode, hit A to select everything, then hit W and select "Remove Double Vertices" in the popup menu.