You can't do both in a single pixel, unless you turn off lighting entirely and make everything fullbright.
Let's have blue-tinted pane of glass, (0, 0, .5, .5). And a red tinted pane, (.5, 0, 0, .5).
Then a blue glow, (0, 0, .5, 0). And a red glow, (.5, 0, 0, 0).
If you have your blue glass glow red, and your red glass glow blue, both combinations come out as (.5, 0, .5, .5).
Under 99% of lighting conditions, it will look wrong. If you put it in darkness, it will look overwhelmingly wrong.
Even if occlusion and emission are the same color it doesn't work. A dark blue object that glows brightly, and a bright blue object that glows dimly, both will have the same RGBA.
Let's have blue-tinted pane of glass, (0, 0, .5, .5). And a red tinted pane, (.5, 0, 0, .5).
Then a blue glow, (0, 0, .5, 0). And a red glow, (.5, 0, 0, 0).
If you have your blue glass glow red, and your red glass glow blue, both combinations come out as (.5, 0, .5, .5).
Under 99% of lighting conditions, it will look wrong. If you put it in darkness, it will look overwhelmingly wrong.
Even if occlusion and emission are the same color it doesn't work. A dark blue object that glows brightly, and a bright blue object that glows dimly, both will have the same RGBA.