Well, exactly fifty years ago, the US Divers company declared that for reasons of surface and underwater visibility, based on "careful research", yellow was their safety "line for '59":
The colour was also adopted around the same time by the manufacturer of the then popular "Skooba Totes" drysuit:
and here in England for Dunlop wetsuits of the same period.
Diving equipment colours later reverted to black, though, which has remained the default colour since the pioneer days. I remember 1960s diving manuals insisting that black items of diving gear, particularly masks and fins, were more durable than the coloured variety. I still have a blue rubber-skirted mask from the 1960s which shows no signs of decay, so I guess that the story was just a vicious rumour circulated by the very conservative diving instructors of the time, who regarded anything other than black equipment as frivolous.
I'm glad that modern gear comes in colours other than black, but I have to say I prefer solid colours. Gull of Japan manufacture fins in a whole range of solid colours:
I'd like to see solid-coloured mask skirts return to favour too. In silicone, only clear and black are on offer, while the choice in rubber is black or blue. No yellows, reds, greens or oranges, though, except vintage masks on eBay. Nowadays' choice of mask plastic frame colours is very much a second-best.
The use of multicoloured "panelling" in suits and fins, apparently today's younger generation "must-have", is an example of "just because you can, doesn't mean you should". Such colour combinations remind me of a medieval court jester's costume:
Court Jester
Design your own wetsuit