A contribution to Becky’s July Squares: Blue challenge.
This is a Common Kingfisher (Alcedo atthis) also known as the Eurasian Kingfisher and River Kingfisher. The colour has been described as blue-green upperparts with pale azure-blue back and rump. I have noticed that the blue colours changes depending on quality and direction of the light falling on the bird.
Interestingly enough, the feathers aren’t blue, they contain no pigments. The colour is produced by the fine surfaces of the feathers interfering with the wavelengths of light. That is presumably why the colours can change depending on the light.