Just a Riddle

Where ever I go I leave a trail behind.
My favorite color is white,
for it is easiest for me to find.

I can do things of great importance,
like hold the key to a fortune and
I can help in leisurely activities.

I can create new imagery or
I can destroy it with only a few slashes.

i have not a long life span
depending on how active I am,
yet to my own knowledge I don't exist.