The Big Prize for the bluest flower will probably be given to Common Chicory (Cichorium intybus).
Below, this colour contrasts beautifully against the cereals ready for harvest that surround it. It can be found in cultivated fields, but also in gardens, on roadsides, or in wastelands.
The stalks zigzag everywhere. No leaves are visible any more, they have fallen off when flowering started.
Common Chicory is a sister of garden chicories and endives and, in fact, its leaves are edible, but very bitter, so you are not tempted to add them to a salad.
To see the flowers you should not wait until the end of the day.
You will not see anything but green stalks, the flowers open only in the morning and early afternoon.