@ jmm1837....I think you are very courageous answering this exceedingly difficult question! The answer above is probably something like I would say. I've been an artist for many, many years but not famous, not well known although I've sold many works and can turn my hand to any style, my preference for my own interest is "in the style of Turner" I've written a book on Colour Mixing for artists which is a teaching text. I'd say that there are not many questions I cannot answer about Colour....with the exception of these kinds of questions....to which, in my opiion, I concur with you, there is no one answer. I often thank my lucky stars that I live in a 1900s timber home that resembles a log cabin inside....Queensland Hoop Pine VJ ceilings, walls and floors, silky oak arctic glass casements, Hoop Pine or Silky Oak doors...and the only colour is the furnishings...and I can't even decide on these! So - to ask me "What Colour" to paint the walls of a house for sale really jangles my brain! I've never had to resolve that dilemma here...I'm not going to paint it...ever! So how to assist in this dilemma? As you explained, jmm1837, older character home -use some colour, newer home with clean lines - light neutrals...so far I agree. BUT...I was watching one of those TV home reno shows...A couple who could not agree on any colour for anything and a designer ,( bless her persevering, understanding, patient, kind, and dog-with-a-bone determination) trying to help them do a reno. I was suddenly inspired ! I had encountered once a colour that contained all colours, that would 'go with' all colours but yet could be described as Lilac but wasn't...and Neutral but wasn't. Thinking "lilac" I think of demure, age appropriate attire and lace...so not very decorator inspiring. The particular LILAC they used for skirting boards, trim and door jams alike worked like magic! I can see readers screwing up their noses and almost hear others saying ERK...That was my reaction when the word Lilac was mentioned.... I did not take any notice what the brand was, I was too astounded by the finished effect. It wasn't Lilac, it wasn't grey...it was a colour but it was a neutral ....and it reflected a different shade depending on its position in the room and its proximity to soft furnishings. So....what's my solution? With both styles of home...think neutral with a tendency to the palest, palest of violetey greys maybe complemented with a drop of ochre ever so subtle...So a neutral to the eye but a colour depending on its position in the house, and keep it all the same, no accents...I believe the light and adjacent furnishings will work with such a hue. Colour is Magic. I'm convinced more than ever that it can morph into any hue. Just some thoughtful reflections from a colour fanatic.

I'd paint all the ceilings with a flat ceiling white.

Same colour as the walls. We painted one door in my daughter's bedroom with blackboard paint.

Suggestions from neutral colours: https://www.dulux.com.au/colour/colour-trends/2018/essential Ceiling & walls the same colour is a good choice for square set. There will be subtle hue difference in various lighting situations anyway, which provides depth and makes for an interesting look.