The 1969 Daytona 500 was the first to be televised in color on ABC's Wide World of Sports,

So, Mopar's winged fleet arrived at Daytona in 1970 in the brightest hues possible.

Bobby Isaac's No. 71 Daytona was a bright red. (It was actually a Ford Motor Company color-Poppy Red-because the Mopar color wasn't red enough.)

The Petty Superbirds were in Petty Blue.

Other Charger Daytonas were painted Sublime Green, Canary Yellow, Onion White, and Plum Crazy Purple

https://www.caranddriver.com/features/aero-warrior

Maybe that is why cars were suddenly in shocking vibrant colors, to be seen on tv in easier to distinguish colors to tell the teams apart at a glance, on the low resolution and small tv screens of 1969.