Clarks (UK) had brake cable housing in a rainbow of cycle colours since the early 1960s at least. I was lucky to score a NOS cable set in authentic Falcon Racing (Baby) Blue on eBay just the other day just in time for the restoration of my '72 Falcon San Remo. Even the gear cable is coated with the proper colour. The package is at the shop so when I get it back, I'll check the range of colours offered but it's pretty impressive. This dates to about 1970.
Certainly coloured housing was the rage in the mid 1980s with yellow seemingly popular. Silver grey is probably the most common for the 1950s, at least British machines. White cable was very common in the 1960s. Indeed, it was the stock colour for Mafac and silver grey for Universal.
Being period correct is hardly "being stuck on details", it's what defines a restoration as far as I'm concerned. But if we err it's often on the assumption older means somehow drab and dull when the opposite was usually the case. Racing bikes have always been the glamour girls, Mercier being a case in point! They had that T-Mobile look 60 years ago.
Peter Kohler
Washington DC USA