It’s the colour of heated titanium. Which may be in the description, I’ve not read anything. When are they launching a 43mm?!
To be clear I don’t want one at all, I meant a 43mm tourbillon in general. They’ve had the same design for this for 7 years (I think?)
I’ve just read two ways to oxidize/anodize titanium. Using heat or voltage. Colors are not technically rainbow but probably close.