Hi Brett about 5 to 10 years ago the trend was if your design style was contemporary your trim colour was the same as the walls and if your design style was classic your trim was a lighter, often white contrast to the wall colour. These days the trend is to the latter regardless of your design style as your builder's designers suggested. However matching your trim colour to the walls is still a good option if you have 8' ceilings. As there is minimal difference (only in the level of sheen) between the skirting boards and wall colour it makes the ceiling look higher. Another option is to do the trim in a similar but lighter tone such as Dulux Grey Pebble quarter. This is a very subtle tone on tone look. Whatever the colour, do you have a choice in the sheen level for your trim? I generally recommend semi gloss enamel on trim unless you are after a more classic look and your woodwork is in very good condition (the higher the sheen level the more any imperfections show up), in which case you could consider full gloss enamel. At the end of the day it's your home so you should do what you'd prefer - after all it's only paint so it's easily changed! All the best with your build.

@ 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.

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.

Do you want the shed to blend in or stand out as a feature? I think Woodlsnd Grey is a good option for you and then you wont have too many different colours...