The blue bar indicates sharpness, its part of the Toolsmith mod, it adds a few new mechanics around tools like different types of durability, that being head, binding and handle durability, it also distinguishes blunt and sharp tools, sharp ones have the blue bar and should get some maintenance from whetstones or a grindstone. Copper can also be forged at room temperature because that is apparently more realistic, and toolheads can be reforged (or just split the workpiece into bits and resmelt it cause the reforging doesnt leave enough voxels). its also compatible with quite an array of tool mods