Answer:
I am lighter than the material I am made of. You see parts of me but more of me is hidden underneath.
I have four fingers and a thumb, but I'm not living. What am I?
I fill a room but take no space.
I am pronounced as one letter, written with three. I come in blue, black, brown, or grey. Reverse me and I read the same either way. What am I?
I jump when I walk and sit when I stand. What am I?
No matter how little or how much you use me, you change me every month.