Excellent workmanship.
BTW, I do believe that the 'yellowing' you all are concerned about is from the light source used to illuminate the pen. Try using anything like fluorescents and see if the colors don't change. Also, it really helps if all lights used are from the same case and/or from the same manufacturer. Not all lights are made the same way and they can even change a bit in different batch runs. Do not mix fluorescents and incandescents either, unless you are trying to get color shifts on purpose.
6000 Kelvin lights are daylight balanced and even in this day and age of digital cameras the colors can become altered. A good graphics program such as Photoshop will allow you to 'balance' the colors to your liking.
Again, Doc, this is a beautiful pen!