Googled the karaka tone - consider resene ash - closest to a creamy white when you see it on the exterior. Depending on your house style, (more cottage like) I'd contrast the karaka green with a near white tone rather than a khaki tone. More modern, more khaki.

Do you have any photos of the front of the house that may give us a better view of the green trim? Have to say that painting costs so much and lasts just so long, you may want to wait until it's needed.

With any post war house built in the 50's the connection from in to out is non existent. Depending on where living rooms are located i would take some of the fantastic windows out and replace them with French doors, or bi folding doors and connect the house to the site. The colour scheme from Karen is perfect to lift the kerb appeal and give it a modern twist. With land costing more than houses these days and the fact that you seem to have quite a big block, after looking at paint colours, opening up the living dining kitchen areas to the outside with a roofed area. Even combining a flat roofed carport which will widen the house to the street making it seem a bigger house, can carry the new look with say an enclosed section for garden equipment, to the opposite side to the house, and if you are lucky enough to have that near the living area it can be used as both car cover and outdoor living. I always think a good landscape architect is worth their weight in gold, to give you a landscape plan, to suit the soil type, your skills level and your preference in planting. Divide up the exterior space to provide outdoor rooms under a tree, paths that lead to some special spot for kids, maybe even a veggie patch with a chock run, and make sure that you use the entire yard, front and back by enclosing part of the front yard in fencing which suits the style of the house, while providing some planting to the street. If allowed a gate structure to blend in with the house, a dedicated pathway with planting each side to the front door, fantastic fencing and consider natural materials like a hand laid stone fence with timber or powder-coated aluminium inserts, to give this house an entry, not sure where the front door is now, so that is not a good look. Gardens always enhance a house, they are never a wasted effort, and if you are not gardeners, make sure the landscape architect knows that and he will be able to select low maintenance plants. All the paint in the world will not give the desired effort that the garden will do to that paint work.

First of all I would like to say it looks like your parents have brought a lovely looking home. The colouring of the outside of the house it typical for it's age. I would like to suggest that you stick with a light tone for the outside but is the Yellow / Cream isn't working then perhaps consider going for a White with a tiny tint of pale green .... this will blend in nicely with the garden, window joinery and roof but it will not be stark white. Internally I am a bit of a cream on cream kind of a person because I like to add colour through my furnishings, knick-knacks etc but I have to say I did move into a home with a mint green carpet which suits my personality but is not all together practical with pets coming and going and a lounge painted a medium to dark mint and I really love that colour. Originally the hall ways and other room where a butter / cream and just making it a off white really boosted the light and spaciousness of the home. The lounge is still the same minty green and I think I will repaint it a similar colour as it is very relaxing and "natural". So go for something that is restful inside and something clean and almost white outside. Hope that helps.