Vinyl dye?

Dying door panels, dash cap, etc.. is simple enough and common practice. Dying headlinners, carpet, seats, steering wheel, is not practicle. You'll wear the dye off the seat skins and steering wheel.
A part like a package shelf board will soak up as much dye as you can put on it.
A complete interior color change is doable, been there, done that. Cost was about a thousand and that doesn't include labor.
I would live with the blue until I was ready to change it and do it right. If you keep shopping for a car that has black or white interior you'll most likely find it needs some seat repairs anyway being 40 + years old.