A friend here in Minnesota had a TT for a while (sold it to another friend in favor of something with lower payments), and we got to experiment with a few things.

The red lense from empeg looked almost orange in comparison to the TT's blood red instrumentation. Looks red elsewhere, but when installed it just seemed orange. I guess it's the VFD underneath adding it's own color to it. The Darkstorm "deep red" lens was much better though. Not perfect, but a lot better for color matching. Unfortuantely being a darker red made it harder to read, though the flip-up "thing" over the radio did help to shade it. Never did try a neon red. Ultimately he went with the standard blue lense, since we couldn't find anything that matched just right, may as well not worry about it at all. This is how I remember it going anyway!

I have a 2001 Mitsubishi Eclipse where I went through something similar. The dash instruments are orange from the factory. I installed red bulbs behind everything though, and when combined with the orange filters (the stock bulbs were just white and shined through these filters) give a nice dark red color very similar to the Audi. I have ended up with the Darkstorm "smoke" lens. For me, his deep red lens was a great match, but also just hard to see during the day (nothing to shade the display like the TT had, and I've got a sunroof that lets a lot of light through). The smoke lens can be read in full daylight, and the green tint it has at night is just not a problem for me. Doesn't match everything else, but the tradeoff of legibility during the day is worth it to me.