I don't have a lot of use for a highlighter, but the Meisterstruck 166 is kind of intriguing. Unfortunately, the only cartridges available are green or yellow, whilst I prefer pink. I wondered if I could change the color of a cartridge... When a reasonably priced marker presented itself, I set to work. Ultimately, it wasn't too hard. My first attempt isn't perfect, but I thought I might share what I've learned so far. 

1. The yellow end plug is easily removed by threading in an M5 fastener and gently wiggling/pulling on it. Just thread the fastener in by hand until it stops turning. The same trick works with a Schmidt rollerball cartridge and an M3 fastener. 

2. The inner ink core is the same diameter as those in inexpensive slim Avery highlighters, but they need to be trimmed to length. I tried cleaning out the original core with alcohol, but i think it's more cost/time effective to just replace the core. 

3. The nib can be removed by gently pulling it out the front. The Avery nib might be able to replace the Montblanc nib, but the wick part that goes into the core seems like it's too short to be effective. I may still experiment another time. 

4. I was able to flush the original nib out pretty well by soaking it in denatured alcohol and agitating in an ultrasonic cleaner. The alcohol and nib went into a baggie, and then the baggie went into the ultrasonic water bath. I changed the alcohol several times and blotted the nib each time before adding fresh alcohol. 

5. To put it all together, I put the core into the cartridge and installed the yellow plug. Then, I aligned and inserted the nib. My nib was still a bit damp with alcohol when i put it in, so I had to use paper towel to wick the alcohol and draw the new ink to the tip. From there, it's ready to stick in the marker body and use!

Overall, it seems like a success. Moving forward, I'm hoping to keep the core inked with fluorescent ink, like the variety Noodler's sells. 

I hope this helps others that might want to make their Meisterstruck 166 a little more colorful!

Montblanc 166 Cartridge Color Change