Which German cars were white? Mercedes-Benz as you went on to say were silver (the "Silver Arrows") and afaik so were Auto Union. USA used white with blue stripes.
British makes used different shades of green. Lotus had a mid green with a yellow stripe, Vanwall was slightly darker. Jaguar and Bentley were similar, BRM was darker metallic (later with the dayglo orange nose), Aston-Martin used a light metallic green, Coopers were dark green with white stripes, and ERAs were anything you like.
Australia and New Zealand (Brabham and McLaren) used variations on the BRG theme.
National colours continued in F1 into the 60s and in some cases beyond, until corporate/brand liveries took over. The first such that spring to mind are the Yardley McLarens and Durex sponsored Surtees cars.
I remeber being given a Yardley McLaren model with a bar of soap and some afteshave. I never got a Surtees model though ;-)
Nowadays only Ferrari and Jaguar still race in national colours. Renaults are blue but that's a sponsor's colour that hasn't changed much since Benetton days.