The frequency of light from a receding light source does indeed change for a relatively stationary observer due to the Doppler effect. This effect causes a shift in the observed frequency of a wave when there is relative motion between the source of the wave and the observer.
In the case of light, if a source is moving away from an observer, the observed frequency of the light will be lower than the emitted frequency. This shift is called a redshift. Conversely, if a source is moving towards an observer, the observed frequency will be higher, resulting in a blueshift.
However, it's important to note that the speed of light in a vacuum, denoted by "c" and approximately 299,792,458 meters per second, is considered to be a fundamental constant of nature. According to Einstein's theory of special relativity, the speed of light is independent of the motion of the source or the observer. This principle, known as the constancy of the speed of light, is a fundamental postulate of relativity.
So, while the frequency of light can change due to the Doppler effect, the speed of light remains constant regardless of the relative motion between the source and the observer. This is a unique property of light and is a key tenet of modern physics.