I'm hoping I'm in the right place for this :3

I've been using the custom HB skin Kalliala, from Roxi (this is the pvp version because I can't find the original link but it has the same skin colour which is the point of this) and I love the colour of it because it matches ElvUI, but my only problem is that I'm so used to having the bars go yellow orange and red as health decreases, it really kicks me into gear with healing

Point is, I absolutely detest having it as green like the default.

QUESTION: Is there a way I can tweak it somehow so that the HP bars are this sort of grey colour at full hp but then go into the yellow/orange/red as health of the player decreases?

Sorry this is sort of confusing but I hope someone gets what I mean o.o