How to: Combining multiple color images with spectral accurate results

I am processing astronomy images and my goal is phot realistic results, but compressing Infra-red to Red and Ultra Violet to Violet.

I have 5 narrow band grey scale images of each object. These images represent the Red (720nm), Green (540 nm), Cyan (510nm), Blue (465nm), and Violet (415nm) channel.

The challange is the Red + Blue does not equal Purple but should slide to Cyan/Green. If all channels have data present for a given pixel the result should be white. 

I am a Photoshop CS6 user.

Thanks,

Mark