In old canon and new a yellow saber is most closely associated with the Jedi Temple Guardians + Sentinel's. The Guardians (specifically had double ended yellow sabers) would give up their identity completely, swearing to secrecy and the protection of Jedi knowledge. Yellow bladed wielders were otherwise thought to have gained most of their used skill/knowledge through scholarly pursuits. But I've read some stuff about this specific era and early on they say a Jedi might change their saber purely for aesthetic, It is supposed to be a peak time for Jedi after all.