David,
I like the cream and I think it will contrast far better with the woodwork on the car, the light green works well on the 401's and 403's but I think would look wrong on the 400 because of the woodwork, a darker green would be better if you wanted to stick with that colour. A good exercise might be to look at the Morris Minor travellers for sale and see which colour you think works best.
If you get a copy of the July edition of the Automobile have a look at the Rolls Royce 20/20 Estate Car that Jonathan Wood has for sale on page 67 or follow the link below you will see why I think cream would work best.
Geoff.
https://www.jonathan-wood.co.uk/for-...25-estate-car/