Though the environment has changed, dust can be destructive depending on where one lives. Reddish Grey - Iron and rust in the dust which can short out electronics if its not cleaned out. Black - a lot of carbon with some acid (Hydrochloric or Sulphuric Acid), which can be corrosive - Trace Rotting. Whitish Grey - animal hair/pet dander. Yellow - Sulphur content in dust, which can go to Sulphuric Acid if it gets wet. So on and so on. Fluffy vs Dense also signifies how much moisture is in the dust content, which for dust with acid can make it more corrosive.
A job like that, I would have picked the dust bunnies cleaned and vacuumed off the rest. Glad you got it working. Yours look like the last - animal hair/pet dander that has broken down long go.
