The ‘Endless Summer’ hydrangea is the only blue mophead which will give me blue flowers here in the garden.  The other macrophyllas are just not bud hardy enough for the Zone 5 cold temperatures of this garden.  It really is true blue in flower and this year, the three Endless Summers looked great but only two bloomed.  I think one is getting just a bit too much shade and some limbing up of the oaks will hopefully resolve the problem.  Clear blue is hard to find in flowers.   Delphiniums

can be clear blue as can gentian,
salvia, and morning glories
but I am finding the fall hues of the aging flowers of the blue hydrangea a mix of turquoise,
mauve
and green. 
They are really quite a bit more interesting than the clear blue.  Are your hydrangea flowers turning color and, if so, what colors are emerging?