Is there any advantage in using color preserver on regular thread vs. NCP thread? If they both look the same why mess around with color preserver?

They DON'T look the same. NCP looks pretty flat compared. It looks like paint. Regular nylon with or without color preserver has a very classy look that sparkles in the sunlight. With the color preserver it will be bright like it is on the spool. Without it it will be darker almost transparent but still have that sparkle.

If you put a NPC and standared thread together. you well notice that the NPC thread is a size larger. A thread looks like C thread. I never use NPC I always put on my own PC .
Keep a tight line Bob

Eric: The choice of color preserver vs NCP or nylon is this. If you are using a dark colored blank such as black, and you put white nylon over it, you will NOT have white thread. What you will have is some shade of gray with cp or without. Without it will virtually disappear. If you want a dominant color, use that color in NCP and overwrap with the color of your choice. If I have an idea for a certain color scheme, and dont know how or question how it will look, I know that I can run a color test on the butt section where the seat and grips will go. Its just going to be covered up anyway. Buy some NCP, nylon, and color preserver. Do your own tests on a butt, and see where it leads you. Traditionally color preserver is applied to NCP thread to help remove pockets of air (which result in bubbles coming thru your finish coats) the color preserver drives the air out in addition to sealing it. When I build a rod for a prespective buyer, I typically run a test like this so he or she knows how its gonna turn out. Color choice is usually the last thing a guy is thinking about when he's shopping for a rod. If you dont use color preserver on nylon, it will bleed. This is not bad and creates some interesting effects. Try it also on your butt section. This is know as the learning curve. You are in it. the Roundman

Very "well said & stated" the points about , above. They are a choice when you get more experienced, also.-