Properly rated safety shields can absolutely be transparent and properly block the necessary wavelengths. The color comes from the wavelengths they're blocking. Weird stance to take that the entire industry is wrong about laser safety.

Lasers emit a known frequency unless they're extremely expensive and designed to create broad spectrums, it's only with cheap consumer units you'll see IR diodes being poorly upconverted to a different color with IR leakage. These cutters use CO2 or fiber lasers and IR is the desired output..