Ok here goes. Physics away.

When you sneeze your water based saliva forms a sperical blob on the monitor. This is due to the surface tension of water. When the three different colored strips of light hit the saliva the saliva acts as a lens and bends the different light away in a different direction instead of blending them into one beam which you recognize as a color.

The equation for this is:
N1 sin theta1 = N2 sin theta2
Where N is the refractive index of the material and theta is angle of incidence as measured from a line tangent to the surface

r       g         b
 r      g        b
  r     g       b
   r    g      b
    r   g     b
    rsssgsss b  
  ssrsssgsssbs 
 sssrsssgsssbss     
ssssrsssgsssbsss
In the illistartion above you can see that the lens like saliva produces a bending affect away from the perpedicular incidence line because it is moving from a material with a high refractive index (saliva) to one with a low refractive index (air). The reason the individual colors appear swirled or distorted is becuase the saliva's surface if not perfectly spherical. If it was you would observe a regular pattern. And the reason it appears to shimmer when you move your head is because different beams of diffracted light line up differently with your eye as you move your head around.

I would do out the calculations but it would be very hard to make the measurements for this on such a small scale. Anyways that is why you see the three distinct colors.
But when I used to sneeze on my Amiga monitor, it magnified pink dots. Do Amiga use a colour combination other than the generic red/green/blue one?

No, Amiga monitors are red, green and blue too. But amiga monitors were designed for a low, fixed resolution, and have a different pixel structure in order to make the picture look less 'blocky'.

PC monitors must cope with lots of different resolutions, and must produce nice sharp lines, so the phosphors are laid out in nice rows, producing nice sharp pixels (in this case, five blue ones, on a white background. The phosphors are each 2 characters tall, by one wide. Just Because.):
RGBRGB--B--B--BRGBRGBRGB
######--#--#--##########
RGBRGB--BRGB--BBRGBRGBRGB
######--####--###########
RGBRGBRGBRGBRGBRGBRGBRGB
########################

On an amiga, this would make an individual pixel look like this
RGBRGB--B--B--BRGBRGBRGB
######--#--#--##########
RGBRGB--B--B--BRGBRGBRGB
######--#--#--##########
RGBRGB--B--B--BRGBRGBRGB
######--#--#--##########

Which would look like a giant rectangle. :(

So the phosphors are laid out in a triangle pattern instead:
 r g b r g b r g b r g b 
g b r g b r g b r g b r g
 r g b r g b r g b r g b
g b r g b r g b r g b r g
 r g b r g b r g b r g b
g b r g b r g b r g b r g
 r g b r g b r g b r g b
g b r g b r g b r g b r g
So a pixel looks like this
 r g b r g b r g b r g b
g b r g b r g b r g b r g
 r g b r - b - - b r g b
g b r g b - - b r g b r g
 r g b r - b - - b r g b
g b r g b - _ b r g b r g
 r g b r - b - - b r g b

g b r g b r g b r g b r g
Which is much more pleasant on the eye. And because the pixels aren't in nice rows, the refracted rays aren't all coming from the same place, so it's more likely that rays entering your eye are from more than one color of phosphor, so the spots won't be simply red, green and blue. Phew!

TVs are also laid out like this. But TVs were designed to display fuzzy demodulated UHF signals, and their pixels are even bigger. If you've got an old amiga monitor kicking around, get a good scart cable and attach it to your sky digital box/playstation. Unfortunately, monitors don't have remotes

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