Trumpers colourings

I have a tub of Trumpers violet shaving cream that is about 2 years old. It still smells great and lathers normally but it seems that the colouring has degraded. Now instead of being the bright violet colour it is blue grey.
What is weird is that the residue on the inside of the lid is still fine, just the main bulk of the cream in the tub has changed. and it is all the way through, not just the surface so it isn't a reaction with the air.
Any ideas?

I don't have any Trumper's shave cream, but I have noticed that the Limes Face Food color changes over time from a bright yellow-green to a more dark and dull color. It also seems to become thinner. As far as I can tell, it does not affect scent or effectiveness.

Now I think of it, I also had that with my samples of the skin food. They both went watery but still worked. I didn't get a change in colour though.