Guessing that the yellow driveline yoke is the one with the yellow spray mark. This would match other C code 65 auto examples I've seen.
1) The color of the second band - Light Blue?
See below
2) Should the red line be there?
We've seen lines (short or long) and X's applied by hand on the tube. Dont' know if this was applied to the tube or to a finished driveline nor purpose at this point
3) Are the stripes and the yellow and green paint correct for my car?
Color of the stripes vary so much (possibly changed often during the first year of production) can can't comment with any confidence. Have examples from about every month Sept 64-Macth 65 V8 automatics and there is not allot of matches between them, plus so few also have legible colors left
4) What does the 4N mean?
Looking at allot of examples believe it identifies the supplier and possible also the plant of the tube marker. Neither month or year fits what has been documented unless the number represents the month
5) Is the counterweight correct or has it been replaced?
Have seen the washer weight before but never considered it an original one in the past. Can't be certain but in over 500 drive line pictures could not find another.