One of the ancestral-like FPs has a green emission and an exceptionally high quantum yield in solution of 80%, which is rare in present day FPs. Even after such value decreased to 76% when the protein was mixed with the polymer composite, such value is still remarkable. Interestingly, the ancestral-like protein has a double value, as it can convert into a red emissive protein upon a stimulus, which is a feature only a few present day FPs have. Even in the red form, the protein still has outstanding quantum yields of 80% in solution and 54% in solid, but the most interesting feature is that, in terms of stability, this ancestral-like FP outperforms any other FP used in the same configuration of device, with even 2-fold with respect to the most comparable FP. These results have an impact in further development for more stable Bio-HLEDs devices, as they can be further engineered for achieving different colors, photoswitching, improvement upon certain additives, chemical modifications, etc.