It's not a "run of the mill bowl". It's gorgeous and it is from earlier times. I don't think they were made post-'80s. Each is completely unique.
They didn't know the cobalt pot was unusual, "precious" or scarce.
They had it, they used it up, then went onto using a paler colour. That's all.
Quite possibly nothing more than not having a bit of cobalt to put in at the time, but having something else to hand.
There were no plans. It was a matter of; "Let's see what we can make from what we have handy".
It was possibly just fluke that a bit of cobalt was around in the first place. I don't know where it might have come from. It's not something I tend to keep in my kitchen cupboards. ;
How we percieve colour is unique to each of our individual brains.