How can my animation animate if there is no vertex weights? I am in the process of creating DirectX Animation Skinning using Blender to Collada.

I am using an animation from an old project, that was rigged, and weighted for animation in Blender.

Whilst trying to debug why my animation skinning is causing all sorts of artifacts, I have noticed while inside Blender under "Weight Paint" almost all of the vertices are Blue.

How then, can the animation in question, animate while in blender correctly, without any weights?

Thank You!
Your screenshot is showing the weights (no weights) relatively to one bone/vertex group only.

Every vertex can be weighted relatively to every bone of the rig (and even to multiple rigs). So, you must check the weight painting of every vertex group of the mesh to see which are the weights. In alternative you can select one vertex and read which are its weights in the "N" properties panel, vertex weights tab.