If you have a GT then you should have HIDs standard. Couple of ways to confirm what you have: 1) Do you have a leveling knob to the left of the steering wheel (should have 0-3 IIRC)? 2) The dust cap should say "high voltage". 3) when first turned on at night the lights take a few seconds to "warm up" to their operating brightness.
Now to comment on wanting that "Blue BMW look".
All cars with OEM HIDs (including BMW) use HIDs in the 4100-4300 kelvin range. That's pure white light, and the closest to sunlight. Lower on the k scale you head towards the yellow/red end of the spectrum, and higher you move towards the blue/purple end. The OEM range provides the most actual lumen output... read: the most usable light. As you move into the blue range (~6-8k) the lumen output drops. Also projecting blue light actually facilitates eye fatigue while driving at night. Will you have an issue with 6000k lamps, no, but still they'll be "worse" than your OEM ones.
If you want that blue look then there are two things you can do to achieve it. 1) Swap out your stock frosted low beam lens for a clear one.... I know they look clear, but the OEM ones are slightly frosted. Doing this will clean up your cutoff and will provide some blue color along the cutoff. 2) Add washers to "color mod" your projectors. Basically add washers to space the lens away from the projector bowl/shield to adjust the projector's focal length. It doesn't change it much, but depending on how much you space it you can greatly increase the color efect on the cutoff.
Doing these two things will substantially improve your output, provide you with that awesome color, and won't decrease your actual light output like swapping to blue lamps would. Many of us Mz3 guys have swapped out to clear lenses with fantastic results. theretrofitsource offers us a direct swap 3" clear lens pair for about $60. Also I know lenses from Evo 8 projectors if in the 3. I'm not sure if the Mz5 has the same size lens, but would suggest contacting Matt at TRS to see if they know the size of the lens, and/or if they know of a lens which will fit the projector (either that they sell or another car's lens which will fit). The install is straightforward. Bake the headlights in the oven (or using a heat gun) to soften the adhesive, and disassemble the housing. Remove the stock lens and swap in the clear on. If you're color modding also then add washers between the lens and the cutoff shield while you're installing the lens. It sounds much more difficult than it actually is and it's really quite easy. Here are some pics of a Mz3 with OEM HIDs, TRS clear lens and color mod.
Washers added
Cutoff
Blue flicker.... sig from a member, best I could find on short notice. The flicker appears/disappears as you move from side to side.