Some thoughts..some sensible, some frivolous.
Fuselage colour.
Anything that keeps clean and hides "blemishes". (my dad is a used car salesman!!)
White is traditionally the go and I suppose fairly cheap because every one gets their planes painted white. Also, if you need to flog them quickly it is a reasonably safe colour.
Light grey doesn't look too bad either.
Any other colour may spook the customer.
Tail and Logo.
A bold colour. Red or Blue seems to be the go. The logo emblem can reflect the country of operation. eg, Ansett has a stylised "star" in it, possibly taken from the Oz flag. (I don't know, just guessing). Qantas has a kangaroo. It can also reflect the company's logo or a stylisation of it. Once again, check out Ansett. Keep that logo for every thing, stationery, uniforms etc. Keeps the association going with the customers.
Keep the logo simple. You want kids to be able to recognise it. "Look Mum, there goes the XXX plane" A mix of these two concepts seems to work well.
Contrasting colour should be subtle but simple. Try gold trim as well. Check out QF's tail for what I mean. Gold is a "safe, secure colour".
Font on the fuselage... Bold and simple. Anything too fancy is a pain to read. Shows up poorly in photographs. I personally find the website emblazoned on the fuselage a bit "off". It must work though.
You are probably thinking "what would I know?" Since we do get a few charter companies into Cairns it is rather frustrating not knowing who the company is. If the tail design is supposed to tell the world who they are then it has have failed if I can't figure out where they are from.
My thoughts only
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If you live long enough, you'll die of something!