Think of it like a sieve; smaller holes catch smaller grains, and here, smaller atmospheric or colloidal particles 'catch' and deflect the shorter, smaller 'blue' light waves more efficiently than the 'long' red waves.

R-B-S: Rayleigh, Blue (short wavelength), Size matters.

When a beam of light passes through a colloidal solution, the particles present in the medium (which are larger than molecules but smaller than suspensions) scatter the light. According to Rayleigh's law, the intensity of scattered light $I$ is inversely proportional to the fourth power of the wavelength: $I \propto \frac{1}{\lambda^4}$. This ensures that shorter wavelengths (like blue/violet) are scattered more intensely than longer wavelengths (like red) by fine particles.

Remember that Rayleigh scattering is defined for particles much smaller than the wavelength ($d \ll \lambda$), while Mie scattering applies to larger particles.