First of all,
Congratulations on your Sailor demo. This is a common problem with Sailor's demonstrators. I have read a number of FPN threads dealing with your particular problem.
-Get onto the FPN Forum that deals with Japanese pens & pose your question there.
-If you can use the Google search function which is found on the top right of FPN's main page, it will list all these threads. There are ways to minimize the stain under your grip/section.
-Do not try to disassemble your Sailor section itself.
It is not a simple operation & you can cause more problems than just having a blue stain under the grip. When you said that you've removed the "nib & feed", I hope you didn't mean pulling the nib & the feed right out from the complete grip/section (as your photo).
Staining may also reappear in this area as you keep using your pen, so do not take it apart.
I have five pens in the 1911 Standard series, but have shied away from the demo pens because of problems like the above. The demo pens are "Kool" to look at, but they are also high maintenance pens, if you want them to look pristine.
Edited by tinta, 08 April 2017 - 19:48.
Sailor 1911 Standards (14c nibs):
*Black/gold, 0.8 mm. stub
*Burgundy/gold, 0.6 mm. "round-nosed" CI & 1.1 mm. CI,
*Sailor Profit Standards: Brown & Red Marbled Mozaiques,(machined acrylic/rhodium),1.0 mm.CI & 0.8 mm. stub
*Kaweco SPECIAL fp 14c."M" "B",(0.5- mm & 0.8 mm BLS)
*Kaweco Stainless Steel Lilliput 14c 0.6- stub (BLS)
*Montblanc 254, 14c "BB" flügelfeder factory stub