Ya, that probably be expensive to have more colors as the amount of paint you will need to buy is more. E.g. you will need 4 litres to finish 3 walls but you can't buy 1L can x 4, it will be very expensive, then you will have to buy a 5L can.
I only bought 2 x 5L can of Nippon Easy Wash, the rests are Vinilex Premium costs S$46 / 5L can. Vinilex does not mean that you can wash, is just not that easy... I don't mind painting it again as time goes by when it becomes dirty as wall is much easier to paint compare to ceiling.
4 x 5L Smart White for Ceiling & Bomb Shelter
8 x 5L & 6x 1L for All walls (Easy Wash + Vinilex)
1 x 5L & 2 x 1L for doors (Bodelac)