1. Green levels 0-255, are how much the value of the reflectionmap is weighted vs. the diffuse map.
2. Red levels 0-255, are how much the diffuse map is raised relative to its final values, after shading (including shadows) is done. IOW, it "glows" because it's canceling out the difference in the angle of the triangles from perpendicular to the sun light.
Glow can and does wash stuff out, though, because of where this occurs in the shader. If you have too high of a glow level, you'll frequently see issues, because the shader allows glow stuff to saturate over the diffuse level. Therefore, I suggest never using a level higher than 220 for red in the glow channel, it leaves some wiggle-room.
Using pure white is fine, and I'm with Smoth, there aren't any shades of white "reserved". I just checked the fragment program, that's just plain wrong.
It caps out at 1.0 1.0 1.0, just like everything else in OpenGL. The issue is that maybe you think that pure white will actually
look pure white most of the time, and the answer is... no, it won't, and should not.
It won't even hit pure white unless the mapper was really stupid and used a pure white light for the sun and a pure white light for the specular highlight... and even
then, it'll only hit pure white if the angle of the normal is on the same vector as the sun. The normal vector's difference from the sun determines how much the sun raises the value over the level of ambient.
You'll only see issues with pure white if you mix it with glow, in which case you'll hit pure white very frequently and wash out the difference between normal angles, because it's adding that value back on top of the texel value
after lighting has occurred. So a pure white area with a lot of glow, facing the sun light, will look really horrible, because the vertexes will wash out, and your model will quit looking 3D.
For a more specific answer, i personally take the RGB (white-black) of the texture and stick it directly into the red channel (glowmap) of my tex2, then cut the brightness by half.
That is completely un-necessary, and totally counterproductive.
Don't do that... do the glow colors in a seperate layer, including the overspill (i.e., the glowy fuzz around lights), then when you make your reflectionmap, you can just fill whatever is there with red value 220, using Multiply, so that all non-red values go bye-bye.
That's the easy way.
Oh, and Saktoth, send me whatever you're seeing these odd problems with, I'll take a quick peek. I'm with Smoth though, it's probably the normals, and that's a quick fix in UpSpring most of the time.