I'm building a Forecast 6' 6" 2 Wt 4 piece and want the thread to blend in to this blank I'm guessing Gudebrod Cobalt Blue my question is should I CP or Not and I plan on using Andy's Lite

Just a matter of preference. No CP will turn the thread much darker and translucent, which many people, including me, really like the look of. Use of CP will seal the thread and keep it closer to its original color. It's up to you. Good call on the Lite, you're going to love it.

Yep ... pick a color a shade or two lighter than the blank and don't use CP, the thread will "disappear" and become very translucent. That has become a very popular effect and it does look sharp, IMO.

I sometimes do a practice wrap on a scrap piece of blank to get an idea of what I am trying achieve.
I personally like the wrap when it almost disappears and then when it gets out in the sunlight it has a subtle color effect

I base my choice of whether or not to use CP partly on whether or not I will be using a trim wrap. With a trim wrap, the ends tucked under the main wrap will show through if you don't use CP. (Because the wrap becomes translucent.) Maybe someone has found a way around this, but I never have.

Rob - I use the nail knot method for trims. No tag ends under the wrap allowing for no CP if that is the look I want.