The reason for this time lag in color change is the particles are becoming more evenly dispersed in the solution. They rearrange themselves to maintain the same distance from each other by virtue of their electrical charge. Once the particles are completely and evenly dispersed, the color will be seen. These particles reflect yellow light while clear CS will not reflect light because the particles are so small. The yellow color comes from the fact that higher PPM CS allows some of the particles to agglomerate together to form a slightly larger particle, allowing yellow light to be reflected while absorbing all other colors.
Agglomeration means some of the silver atoms are starting to share electron rings.
If you could turn that 1 milligram into 1 million individual silver particles and disperse it in the water, the PPM is still 1. However you now have many more individual pieces of silver in the water to attack bacteria and viruses. If you could divide that 1 milligram of silver into so many pieces they barely reflected any light, then you would have the optimum amount of silver per unit measure of water. Typically those particles are about .001 to .005 microns in diameter. Pretty small particles indeed.