Some of the many forms of G. himalayense and/or G. pratense may be closer to the "cooler blue" that you are looking for. These plants are however, typically much larger than the 'St. Ola' (G. Ã cantabrigiense) you have.

In addition to the popular 'Rozanne', I've always been a big fan of G. Ã magnificum, although this is also likely too dark of a purple-blue for what you prefer.

'Brookside', 'Orion', 'Jolly Bee', 'Rozanne', 'Amy Doncaster' and 'Mayflower' are all geraniums on the blue-er side. However they are all taller than 'St.Ola' and bloom at various times. I also grow G. magnificum 'Rosemoor', but it is more of a purple-blue.