It hasn't. There is something "wrong" with the image in Dr. Becky's video. In other words, the image of Albireo has been processed, or filters have been used, in such a way that Albireo has been made to look blue. It doesn't in reality, not to the human eye!
Constellation Cygnus with Deneb and Albireo. Photo: Tony Hallas.
Take a look at this picture by Tony Hallas. The colors have been saturated, but they are "true". As you can see, Albireo looks yellow, not blue.
I remember way back when, when I saw a starfield photographed in infrared. Since infrared wavelengths are invisible, the stars had been given mapped colors. Two enormous blue stars stood out proudly, and I was so intrigued. What stars were they? How could they be so blue?
Well, disappointment of disappointments! They were two red giants of spectral class M!!!
These cool stars were just hot enough by infrared standards to be mapped as blue!!So something has been done to the picture of Albireo to make it look blue in Dr. Becky's image, but it isn't blue in reality, believe me!
Ann