Part of being a lampworker is that undying desire to 'find new glass', not just new colors - but what they're calling reactive colors. That is, when one color is put onto or up against another color - some sort of chemical reaction takes place - and there is some drastic change in state.
This focal bead is one such example. For one of the glasses to achieve it's calling in life - it has to have an oxygen rich flame, whereas the other needs a propane rich flame. Since there is no pleasing both because of their close proximity... one 'suffers'. The original idea was to try to please both, but in the end, the effect was rather dramatic and pleasing.