I don't know what you mean by "Thermal Vision,"
It looks like you are using Rotobrush. Purple line is normal.
There are some icons at the bottom of the layer panel that allow you to select different displays of the mask. It would really help if we knew with the footage was supposed to look like.
I have another suggestion for you. When you were doing labor intensive work like Rotobrush or rotoscope it is usually much more efficient to put just the footage you are working on trimmed to in and out points plus a couple of frames in case you need them in a separate comp so you are only working with the actual frames you need to be spending time with. This lightens the load and usually makes the world go faster. When you finish the Roto you can nest The comp in your maintop to finish the composite.
If I need to Roto a shot that is more than seven or eight seconds I almost always render the results and replace it in the project. This can save you hours if something gets screwed up.