I’ll stick my neck out and say… 1994. I know, not the best year safety-wise. But livery-wise, it was amazing.
The multi-color Benetton
The Rothmans Williams
The scarlet red Ferrari
The red and white McLaren
The black Sauber
The techno-Technicolor Footwork
The black and yellow Minardi
And those are just the best ones! There are many more that come to mind.