The answers to many of the questions you ask are in the NASA technical literature. Go have a look at it; it's vast. (Would an organization trying to protect a massive hoax release so much data?)
The site is the NASA Technical Reports Service,
http://ntrs.nasa.gov/You will have to know what you're doing and what you're looking for; most of these documents were written by working scientists and engineers for other scientists and engineers, not the general public.
Among the most interesting (IMHO) of the Apollo documents is the series of Apollo Experience Reports put out toward the end of the program. To this engineer, at least, they are surprisingly readable and give a lot of useful advice to anyone contemplating doing it all over again. (I'm sure they were required reading for engineers working on the Constellation program).
In Apollo Experience Report - Development of the Extravehicular Mobility Unit, NASA TN D-8093, on page 20, is a table showing
all of the relevant thermal and optical properties of each layer in the LEVA, the Lunar EVA Visor Assembly (?). The astronauts put them over their pressure helmets during EVA to shade the sun, block harmful ultraviolet (UV) light, cut glare, and reduce the external heat load on the life support system. Cooling was provided by evaporating a limited supply of water into space, so conservation was important.
Rather than just retype all the numbers here, I'll discuss a few that may be of interest.
Under the LEVA was the pressure helmet, the same one worn inside the spacecraft when needed. It was obviously not removed during EVA. It was made of Lexan (polycarbonate) plastic. It is practically transparent to visible light (92%), moderately transparent to near infrared (68%), completely opaque in the far infrared (0%), and dark but not opaque in ultraviolet light (18%).
The impact protective visor, worn over the bubble helmet, transmitted 63% of visible light, 37% of near infrared, but no UV or far IR at all. Because it completely blocked UV, this visor was always in place during an EVA to prevent sunburn and eye damage ("snow blindness").
The impact protective visor was still fairly transparent to visible light so you could see in shadow without too much trouble. But for the same reason there might be too much glare in sunlit areas so an outer "sun" visor was also provided. This is the gold one most famously seen on the astronauts on the moon. It transmitted only 19% of the visible light and even less (12%) of near infrared so it kept a lot of the sun's heat out of your face and the cooling system.
The gold visor was just like a pair of sunglasses, up to the wearer to use or not. Many astronauts lifted it to see in the shade, as the Apollo 11 astronauts did in the LM's shadow, and then dropped it when going back out into sunlight.
Remember that even with this gold visor up, the inner visor and the helmet still provided excellent protection against ultraviolet sunburn and eye damage.
On some of the later missions, especially Apollo 17, the visors quickly became badly scratched by the highly abrasive lunar dust. On TV we can often see Jack Schmitt, especially, often raising his visor while in sunlight simply to be able to see clearly.