The "Tommies" are at their peak about now and have been particularly splendid this year. My favourites are the paler ones possessed of a soft shimmering violet hue but there is considerable variation in the palette of Crocus tomassinianus  (including the pure white form I mentioned a few days ago).

 The ones in the lawn are mostly a deeper magenta tone (also very lovely) and among them there is a scattering of a form which is altogether darker and richer in shades of plum-purple. These seem to come into flower a tad later than the lighter ones.

 Interestingly a yellow crocus is starting to spread among the Tommies. I seem to remember one or two of these appeared when I planted the lawn with C. tommasinianus and I assume they had slipped into the batch by mistake when they were packed. They seem to like the same environs and are starting to multiply.
 I think the subtlety and simplicity of tommasinianus far preferable to some of the larger, rather gaudy cultivars that have been developed by plant breeders. That said there are other wild species which are very striking and sometimes almost lurid in colour (in a good way). NB It's worth noting that crocuses are introductions to the UK -mainly from the continent- going back to at least the middle ages 
 Back in March 2017 I wrote about a visit to Church Lane in Tottenham, North London where there is a vivid display of spring crocuses on a long grass verge. No-one seems to know how it came to be there and the assumption is that it's an ancient colony that has survived from when the area was a rural parish outside of the city.
 It's significant enough to be mentioned in Richard Mabey's 'Flora Britannica' who notes that it includes C. tommasinianus, vernus, kotschyanus, speciosus, biflorus and crysanthus- and that the last two have cross pollinated to create a "hybrid swarm" of variations...