Blue is generally considered more whitening than grey. This perception is based on the psychological and physiological effects of color on human perception. According to a study published in the Journal of Environmental Psychology, blue is often associated with cleanliness and freshness, which contributes to the perception of whiteness. Grey, on the other hand, is often associated with neutrality and dullness, which may not evoke the same sense of brightness and cleanliness.

The color blue has a higher saturation and lower value compared to grey. Saturation refers to the intensity or purity of a color, while value refers to its lightness or darkness. Higher saturation and lower value in blue make it appear brighter and more vibrant, which can enhance the perception of whiteness. Grey, with its lower saturation and higher value, tends to appear more muted and less bright, which may not contribute as effectively to the perception of whiteness.

A study conducted by the University of Alberta found that participants rated blue as the most effective color for making a surface appear cleaner and brighter. This aligns with the concept of color contrast, where blue's high saturation and low value create a stark contrast with darker or less saturated colors, making the surface appear whiter.

Furthermore, the cultural and historical context also plays a role in the perception of color and whiteness. In many cultures, white is associated with purity and cleanliness, while blue is often associated with tranquility and calmness. These associations reinforce the perception that blue is more whitening than grey.

In conclusion, blue is generally considered more whitening than grey due to its higher saturation, lower value, and cultural associations with cleanliness and freshness. This perception is supported by scientific research and aligns with the principles of color theory and contrast.