Adults having green snot is a bit different than young children as their sinuses don't function the same.
Also, having no snot at all can still be an infection!! My baby had bronchitis or pneumonia (not sure, dr said take abx and bump up his breathing treatments and gave oral steroids which we've had with a pneumonia diagnosis in the past) and hardly any runny nose at all. Very croupy though. :-(
I would increase fluids, steamy showers, saline/suction and just keep an eye out.
Kristi, Mommy to Josh & Nick (identical twins 6-97) Nathen (3-02), Joey (2-04), Jacob (11-05) & Aaron (12-11) I sell Tupperware!
"A person's a person, no matter how small..." Dr Seuss