Blue, green or red?
The simple rule is this: look at the colour in your expansion tank, or at what the manual specifies. Blue takes the blue, green takes the green, and pink or red takes the red. We sell all three versions of Valvoline Zerex and all three cost the same.
By brand
Blue: Subaru, Honda, Acura and those Nissan and Infiniti models that carry blue factory coolant.
Green: Hyundai, Kia, Mazda, Mitsubishi, Suzuki, Isuzu, Daihatsu, Daewoo and those Nissan and Infiniti models that carry green factory coolant.
Red: Toyota, Lexus, Scion.
This is a general orientation. Always verify in the manual, or simply look at the tank, because the same brand can carry different specifications across markets and generations.
For Subaru the answer is unambiguous: a Subaru needs the blue, since its factory long-life coolant is blue too.
You no longer need to fill the wrong colour
The choice used to be between two colours, and filling a green or a pink system with the blue was a compromise: valid by specification, but you lost the colour and with it the information.
Now we carry all three. For a green system take Valvoline Zerex Asian Green, and for a pink one take Valvoline Zerex Asian Red. The colour stays meaningful and the chemistry is exactly what the manufacturer asks for.
One rule does not change: never mix two different products. Pick one and stay with it.