Soda Lime or regular float glass, are all normal green house windows.
Optiwhite, crown glass, borofloat, pyrex, and borosilicate are all clear. It is also known as waterwhite glass.
Getting it clear is only half the battle, typically clear will get you to 91.6% of the light passing through, the next step is to go for doublesided AR (anti-reflecitive) coating. Depending on thicknesses, AR coated window glass (which is green), passes more light than the clear glasses without AR coating.
Okay, so, what type of glass do you have in your hand, turn it on edge, and look from the edge to inside the glass. If it is green, you have soda lime float glass. (otherwise known as window glass).
Soda lime float glass (a.k.a. window glass) that is often used in flashlights causes a shift in emitted light towards the green portion of the spectrum. So you could have the whitest white emitter shift out of the perfect white bin into another bin when using it, depending on where it sits in the bin. How far it shifts will depend on the glass thickness.
I should run a test one of these days to see exactly how far the soda lime float glass actually shifts the light color, on top of dropping the light output level.
Without AR coating, you have a 3-5% drop in light output (typically 4%) for each face, for a total of 6-8% loss, on top of 30 - 15% typical losses for common flashlight reflectors. You can drop the reflector loss to a total reflector loss of 2 - 15% when you go to lab or telescope quality reflector coatings.
You can make an aluminum reflector from 100% pure aluminum (the normal aluminum you get is not pure but an alloy), and get the reflectance up to 93%, by putting a perfect polished surface on it. Unfortunately, on contact with normal air, it rapidly degrades from this immediately.
This is why they do it in an inert atomsphere, and do a special protective oxide overcoat. Most of the oxide overcoats will degrade the reflectivity. Some special oxide overcoats will actually improve the reflectivity.
Nickel makes for a rather bad reflector surface, at 72% reflectivity, though it does not degrade much on exposure to air, though it is commonly used for reflectors.
http://environmentalchemistry.com/yogi/periodic/Ni.html
Though you can get a rather specialized hi phosphorous Nickel that is rumored up to 80% reflective if it is done properly.
Also if looking this stuff up, note that solar reflectance, and normal reflectivity are two different numbers, and even the folks that use the terms get them mixed up. Solar reflectance includes IR and UV reflectance, though some only use visible + IR to make the numbers look better. In the end, it is always best to ask for a graph of reflectivity vs. wavelength.
Add all this up, and thats where flashlight manufacturer's claims that use the light source lumens for the flashlight lumens are easily 30-50% too high. Very few actually measure it.