How do I blend colors the expected way?

[Lab Rat]

I have a question that should be easy to answer. In Illustrator CS4, if I have a blue object overlapping a yellow object, and I want their intersection to be green (as most people would expect), how do I do this? Right now it defaults to grey, and changing the blend modes doesn't give me the effect I want.

Surely there must be a way other than manually faking it, but I can't find it. Help?

[grnofslt]

One way to do what you want is to draw your two shapes with one overlapping the other with each object having the color you want. Select both objects and using the Pathfinder Panels command for Divide in the Pathfinder section of the panel. You won't see any change but Illustrator did divide your objects and group them. Click on the section that overlaps until you see that you are in isolation mode. Click once more on the overlapping selection to select it and change the color to the color of your choice.

There are probably a good number of other ways of doing this but that is the benefit of having a program as good as Illustrator in your tool box. So many ways to do the same thing. Ya gotta love it.

[Lukas Engqvist]

Blending is maths, and so blending goes from the one set of numbers to the other.
In CMYK blue is CM and Yellow is Y, so foing from 100 100 0 0 to 0 0 100 0 will give you 50 50 50 0 in the middle, a gray.

In RGB, Blue is B and yellow is RG, and a similar situation occurs.

You can add intermediate objects, colour them your green and then blend.
Eg blending a 100 100 0 0 to an object 0 100 100 0 to 0 0 100 0.
Add any number intermediate steps.
1704

Opps didn't read correct.
Well the maths is still the same. Now what you are doing is thinking some medium rather than thiking maths.
Still what colour mode you are working in does affect the results. RGB mode is probably more logical, Illustrator does not allow you to use HSB as working model, which is what you are expecting.
Now also in the real world depending on what kind of paint you use you will get different results.

I would suggest selecting the objects. then using Pathfinder divide, and fill the objects as you please or use the Live paint function and fill wit the colours "you would expect"