Material effect : Mixing Red and Green light emits Blue light resulting in white

Hi,

I bought two colored outdoor LED lights, one red and one green. I made a picture of the result on my balcony fence, that when red and green light is over a certain threshold, the white paint emits blue! Is this effect possible using Blender 3D today?

According to the schoolbook mixing red and green light should result in yellow, but in my case I get white!

What do you think?

See attached photograph!

--HPS