Actually, I'm not quite sure where this argument is going. I'd had in mind that I would be able to say something along the lines of Hirst's painting containing so much less information, and that therefore the value of Hirst's is almost entirely in the context, whereas Degas's contained lots of information within the painting. I'm not sure that is coming out quite so clearly.
I think the point is that it depends on how important the exact colours of each of the spots is. If the exact colour really matters, then the difference in the number of bits required for the Degas and the Hirst is not so great (assuming, of course, that the precise colour of every touch of Degas's paint brush is not equally important). If, on the other hand, it is sufficient that the dots are a range of colours, then my program which generates random colours is fine, and, with a little tweaking and zipping, I got it down to 381 bytes. I'm sure it could be reduced much further, but that's not the point, I'm interested in 'orders of magnitude' here (though I'm tempted to do something in Mathematica for the fun of it). Or I could just say "Paint circles in a 13 by 11 array, each circle x mm diameter and spaced by y mm in each direction and each circle a different colour". That's 133 characters (including spaces), so needs a 133 bytes. There's lots more to consider about the context here. Like that you already know what the words 'circle' and 'paint' mean. Anyway, my argument is that you could not describe the Degas in the same way.
Of course, there must be more to the Hirst - the type of paint, the paint surface, the brush strokes. I need someone to explain the Hirst to me. To tell me its story.