Mixing Light a la Seurat?

Following a talk by Hilary Dalke I have been wondering what the effect of multiple small light 'spots' of enclosed colour would be from a distance. Also tubes of different coloured light laid side by side...

Caroline asked if multiple light sources side by side would appear white? This was in response to Hilary's description of her own early paintings where she ruled coloured lines close together that, from a distance, appeared brown - an undulating mass of brown. This effect occurred because mixed primary pigments always appear brown. Simply put, when the brain sees multiple colours it 'mixes' them and perceives the resulting colour.

So would interleaved primary light sources appear white? Red, green and blue light make white light. This is easy to simulate, and stage lighting relies heavily on the effects caused by mixing in this way.

But laying different coloured lights side by side is rather different. Where the coloured glow from one light overlaps with the glow from another there is a mixing of light and another colour is seen. But would red, green and blue lights or light sources become one white mass?

The effect would be different if the light sources were enclosed than if the light were allowed to spread out over the juxtaposed lights. My feeling is that in the first case we would not perceive white light, but that we possibly would in the second. The only way to find out is to try it...