I believe your problem is that you don't have the factor of the Invert Color node all the way up to one. Your third screenshot shows the Invert Color factor is set to ~0.483.
With the Invert Color node at zero, it just uses the original color.![zero inversion](https://cdn.statically.io/img/i.sstatic.net/2fN5IrzM.png)
Invert Color set to exactly 0.5 exactly blends the color halfway, leaving it completely washed out.![half inversion](https://cdn.statically.io/img/i.sstatic.net/2fU2I5GM.png)
Even turning the contrast up all the way on the Brightness/Contrast node makes no difference, as there isn't even any data to make more contrast-y.
![half inversion full contrast](https://cdn.statically.io/img/i.sstatic.net/KPs7CwmG.png)
Setting it all the way to 1 completely inverts the color, restoring the original contrast, but inverted.![full inversion](https://cdn.statically.io/img/i.sstatic.net/EVeFG6ZP.png)
I hope this clarifies your issues. Unfortunately, I don't have the materiel you used, so it's hard to know if this is what you encountered.