Thanks for the replies, sorry it took so long to respond. It occurs to me that some more information would be handy, so here's a highly accurate engineers drawing of the apartment:
The model Railway will most likely run along the wall at the top, all the windows are at the bottom.
I suspect the architect spent a total of about fifteen minutes designing this apartment; at a guess one switch operates lights 1,3, and 4; and the other operates 2 and 5.
My initial thought was to use LED floods in position 4 & 5 with a filter to diffuse the light, or even to bounce it off the window/door wall to make it more diffused; the wall is painted white and the windows have a frosting foil on the windows which would bounce the light well.
To get around the question of colour and make the lights independent of the existing circuitry I was looking at something like these
LED floodlights. They have a 120° range, and RGB capability.
The disadvantage of this is that they would project shadows on the wall. Any thoughts how I could deal with that?