What does the color of the coolant indicate?

Question

I used to have a car (1989 Opel Vectra) where the coolant was green. However, for my two newer cars (2011 Toyota Yaris, 2016 Toyota RAV4 hybrid) the coolant is pink.

What does the color of the coolant indicate? Is it an inherent property of the chemicals used in the coolant or some coloring added to distinguish between different types of coolant?

Are there other possible colors than green and pink?

If two coolants have the same color, is it enough to indicate compatibility with each other?

Answer 1

They are attempts by different automakers to color-code different types of coolant, mainly for the benefit of their own dealers' service departments. It is Not a perfect or standardized system and should not be relied on. Get the coolant type specified in the manual.

There are different types of coolant because of changing materials in engines, and what automakers have learned about long-term maintainability. for instance, the modern coolants don't need to be changed annually.