I’m working on a house in Unity.
I want my clients to be able to change the colours of walls etc. That’s fine - I know how to set that up with a GUI.
My problem is, how do I ‘save’ their choices so that when they close down the game and open it again sometime later, their choices are still there?
If it is a single-player game, you could write the information you need in one or more files. A better solution (that would be compulsory if your game is a multi-player a game and you need some kind of persistence) would be to write the information to a database. When the game start (or when the player enter in a scene), you should read the data you need from the files or the database where you stored the information. Then, you can change the colors of the walls in scripting depending on the values that you’ve just retrieved.
I’d just use Unity’s built-in PlayerPrefs for this sort of thing:
http://unity3d.com/support/documentation/ScriptReference/PlayerPrefs.html