"Blue Border"
Following a lead from Jacques Vallee's Forbidden Science Volume 5, where Col. John Alexander supposedly stated that "Blue Border" was a level of special access that could "get people killed", I began digging into this. However, I eventually set it aside as I seemed to hit a dead end in linking the information I found to UAP activities or programs.
That was until recently when I stumbled across this tweet from @ChrisUKSharp in the context of why David Grusch had been unwilling to go into detail with DoD's AARO about what he knows regarding the UAP/UFO programs. He seemed to be concerned about how extremely sensitive intelligence information would be handled if divulged to them.
This immediately stands out as likely being in reference to the "Blue Border" series of documents within CIA DDO (Directorate of Operations), reserved for extremely sensitive HUMINT intelligence. Chris also mentions that this is "non-UAP related but adjacent."
"Blue Border" is a special compartmentalized access for the highest sensitivity intelligence obtained from Human Sources within the CIA. This is somewhat similar to how BIGOT listing would function when placed onto certain special access programs to compartmentalize information, except in this case, it is even more restrictive than a BIGOT list control system.
"Blue Border" series reports have a blue stripe on them and are personally signed by the CIA director. These are also provided in the PDB (President's Daily Briefing) from time to time.
It seems clear that the contents of the "Blue Border" reports themselves don't necessarily have to do with UAP in order to be labeled as such. So, what did Grusch find that was "non-UAP related but adjacent" within this "Blue Border" intelligence that would still be relevant to the topic in a HUMINT capacity? Especially at a level where he needed assurances from AARO to handle it properly?