Half March, when temperatures are rising, the moor frog males (rana arvalis/heikikker) literally get the blues. They tumble over each other, make bubbling and barking sounds, enjoy the sunlight and try to impress the females with their stunning lavender-blue colour. This picture nicely shows the various stages of warming. Although it remains strange that warming is indicated by the cool colour blue.
Exif: F 5, ISO 400, 1/500 sec, 250 mm.