From reading your other thread, your tank has been set up for a few weeks.. And you have added livestock.. At least a week ago. So, you have material to skim.. There is a lot that goes on besides just skimming out the food that we add to the system.. Just the biological functions alone can bring organic matter.. So, the tank being new, nah.. You should still have skim..
And the color, that is going to be determined by the settings of your skimmer.. Not how old your tank is.. We have to remember, even on the best day, none of our tanks are sterile and/or lacking in activity. Whether we see it with our eyes or not..