Is the issue that the red color is not saturated enough, or is it too much, as your first two shots don't look bad to me. I kinda like the red light. But I don't know what you're looking at or what you're looking to accomplish. But first, I'd agree that your camera needs to come off of programmed exposure if that's how you're using it. IIRC from a G8, there is an exposure compensation dial on the top. Put the camera in aperture priority automatic, set it on a tripod, and, if you're shooting indoors, set the aperture wide open. Try a shot with the compensation dial set at 0, then begin adjusting it to add exposure in 2/3 stop increments (should be every two little white notches on the dial) and take another shot. I've generally found it takes +2/3 or +1 1/3 stop to open up the blacks.
Also, it looks from the centered white highlight that you're using a flash - try turning that off first and use the available room light. That will definitetly require some plus exposure compensation. (You can try angling a piece of white poster board in front of the amp to bounce ceiling light back up onto it. Just be sure the poster board stays out of the picture.)
If you're shooting color, filters of any kind will cause the entire photo to be whatever color the filter is, be it green or really dark red, which is the color of an infrared filter. Since a digital sensor sees color only, that won't work. There are a few cameras out there where the sensor and associated electronics have been modified to see only infrared light but that's usually only an option on some high priced pro cameras.
And finally, even with all that, post processing, as mentioned earlier, may be your only salvation.
Edit: one other thought. The digital exposure mantra is to expose for the highlights (in this case the red meters) and process for the shadows. Using a fill card (the big poster board angling light to the amp) will help decrease the exposure delta between those shadows and highlights, making the post-processing a bit easier.