The colours are 'infinitely' sub-scalable, but the plot-point shapes are not (there are only so many ways to draw a triangle or circle without appearing identical). And yes, standard R plot-point shapes are limited to a collection of 25, so at least now they are re-used when there are more groups, which is not ideal, but each group still has its unique colour. A plot with 25+ groups becomes almost illegible anyway, so we are dealing with extreme use-cases here I believe.