The mirror of the James Webb Space Telescope was plated with gold for a better reflectivity of infrared light. It reflects also red light well but not blue.
Conventional telescope mirrors were plated with aluminium for better reflectivity of visible light.
Would it be possible to combine the reflective properties of gold and aluminium (or silver) for a good reflectivity from infrared to visible light, even ultraviolet? For a future telescope with multiple sensors to cover infrared to ultraviolet light.
The metals may be combined as an alloy or several very thin layers of alternating metals.