The 1dB attenuator will eliminate the red push, but the service menu tweaks also let you line up green as well. If you're not comfortable going into the service menu, then the 1dB attenuator is a must.
No, the service menu tweaks do NOT affect HDMI, because the color decoder isn't used on a digital connection. The reason you have a color decoder is to recreate color from the analog signal of composite/S-video/component video. With a digital connection (DVI, HDMI), the color levels are sent as a digital value instead of having to be decoded. In other words, so long as your source doesn't mess with the colors, you should get accurate color from HDMI.
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