ZA-SAMO 2022 Problem 5

Let $n \geq 3$ be an integer, and consider a set of $n$ points in three-dimensional space such that: [list=i] [] every two distinct points are connected by a string which is either red, green, blue, or yellow; [] for every three distinct points, if the three strings between them are not all of the same colour, then they are of three different colours; [*] not all the strings have the same colour. [/list] Find the maximum possible value of $n$ .