Why are Pigment Spots Different Sizes?

[LadiesMan]

1. Why are some pigment spots larger (area and volume) than others?


I understand that pigments move up the porous paper by capillary action, from research. But why are some pigment colours (areas) larger? THanks

 

[LtStorm]

I'd think the area being larger would mostly imply more of the pigment was placed on the paper. I imagine a very small volume of difference between drops of two pigments would cause a still noticeable difference in the size of the spots.