Alright so I follow and amazing photographer on Instagram and he shoots a lot of his images with an umbrella mounted from above. He is using a white backdrop seamless paper. The umbrella is the only light he's using for the most part and might add another smaller softbox mounted directly in front of the model for fill. When you see his images in his videos, the white background looks blue or light grey. He tethers his shots into Capture One. Do you think he might be using a preset in Capture One to change the background color or is it something he could be doing in camera? As far as I can tell from watching his videos, he isnt using a blue gel with his light. The question has come up several times in the comment section and he conveniently ignores them. I am sure it has to do with his style and all but I am curious how its done if no gel is being used.

if his light is primarily lighting the model and not the backdrop the backdrop could be appearing grey simply because he is preventing the light from illuminating it to its true whiteness.

Or he could be adjusting the backdrop colour with software.

"I am curious how its done..."  Have you considered leaving a comment on the actual IG image you're curious about? IG folks tends to be a very colloquial crowd.... Lot's of friendly exchanges in the comments section on posted images.

However if you are interested in how I handle background illumination (or how my clients (as a commercial makeup artist) address this issue) then the lion's share of my video clients use Green Screen... Since you do IG reels believe you're not naive here.   

Chuck my choice? Depends on our client's expectations (which I always explore in our initial consultations) You would be surprised on how this plays out... many times both my client and I ultimately arrive at a scenario that neither of us came into the consultation with.  Also in my pre-shoot consultation with our team members on the assignment we address same (with contingency plans as needed) .

That said, I'm a major fan of Black Velvet... I've got a huge 8 foot wide roll of same I purchased several decades ago... I store this tube of Velvet vertically so as not to crease it.  It has paid for itself many times over. 
However I am also a major fan of High Key and as such have a Giant Octa and a 30x60 SB I use to go 1.5 stops over my Key to provide white backgrounds without detail (245-245-245)

btw, I'm not a major fan of White Seemless... marks up so easily and I shoot a lot of ballet with aerial moves and those pointe shoes go through a roll of White Seemless very quickly.  If I have to do seemless it will be gray... Experience is a brutal teacher at least for me albeit I'm certain many others may have different experiences here... Totally understood...

Disclaimer: Since a considerable portion of my revenue stream comes from Bridal Makeup thus I avoid any set configuration or genre that might not be well received by a MOB... Who nearly always is the individual who signs the check. a.k.a. I keep everything conservative as possible (including backgrounds). Hope this makes sense Chuck. 

Wishing you much success on your photographic journey...